diff --git a/src/OpenApi/gen/XmlCommentGenerator.Emitter.cs b/src/OpenApi/gen/XmlCommentGenerator.Emitter.cs
index 82864654e936..5538f0163d2d 100644
--- a/src/OpenApi/gen/XmlCommentGenerator.Emitter.cs
+++ b/src/OpenApi/gen/XmlCommentGenerator.Emitter.cs
@@ -57,6 +57,7 @@ namespace Microsoft.AspNetCore.OpenApi.Generated
     using System.Threading.Tasks;
     using Microsoft.AspNetCore.OpenApi;
     using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
     using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
     using Microsoft.Extensions.DependencyInjection;
     using Microsoft.OpenApi;
@@ -153,30 +154,6 @@ public static string CreateDocumentationId(this PropertyInfo property)
             return sb.ToString();
         }
 
-        /// <summary>
-        /// Generates a documentation comment ID for a property given its container type and property name.
-        /// Example: P:Namespace.ContainingType.PropertyName
-        /// </summary>
-        public static string CreateDocumentationId(Type containerType, string propertyName)
-        {
-            if (containerType == null)
-            {
-                throw new ArgumentNullException(nameof(containerType));
-            }
-            if (string.IsNullOrEmpty(propertyName))
-            {
-                throw new ArgumentException("Property name cannot be null or empty.", nameof(propertyName));
-            }
-
-            var sb = new StringBuilder();
-            sb.Append("P:");
-            sb.Append(GetTypeDocId(containerType, includeGenericArguments: false, omitGenericArity: false));
-            sb.Append('.');
-            sb.Append(propertyName);
-
-            return sb.ToString();
-        }
-
         /// <summary>
         /// Generates a documentation comment ID for a method (or constructor).
         /// For example:
@@ -389,7 +366,7 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     foreach (var parameterComment in methodComment.Parameters)
                     {
                         var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
-                        var operationParameter = operation.Parameters?.SingleOrDefault(parameter => parameter.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
                         if (operationParameter is not null)
                         {
                             var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
@@ -400,7 +377,10 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                             }
                             targetOperationParameter.Deprecated = parameterComment.Deprecated;
                         }
-                        else
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
                         {
                             var requestBody = operation.RequestBody;
                             if (requestBody is not null)
@@ -449,10 +429,14 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     && metadata.ContainerType is { } containerType
                     && metadata.PropertyName is { } propertyName)
                 {
-                    var propertyDocId = DocumentationCommentIdHelper.CreateDocumentationId(containerType, propertyName);
-                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyDocId), out var propertyComment))
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
                     {
-                        var parameter = operation.Parameters?.SingleOrDefault(p => p.Name == metadata.Name);
+                        var parameter = GetOperationParameter(operation, propertyInfo);
                         var description = propertyComment.Summary;
                         if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
                         {
@@ -499,6 +483,86 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
             return Task.CompletedTask;
         }
 
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
         private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
         {
             if (sourceParameter is OpenApiParameterReference parameterReference)
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/OperationTests.Controllers.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/OperationTests.Controllers.cs
index ef26c9590ec3..72610d6beb79 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/OperationTests.Controllers.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/OperationTests.Controllers.cs
@@ -141,4 +141,173 @@ await SnapshotTestHelper.VerifyOpenApi(compilation, document =>
             Assert.Equal("The id of the user.", path.Parameters[0].Description);
         });
     }
+
+    [Fact]
+    public async Task SupportsParametersWithCustomNamesFromControllers()
+    {
+        var source =
+"""
+using System.Collections.Generic;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.DependencyInjection;
+
+var builder = WebApplication.CreateBuilder();
+
+builder.Services
+    .AddControllers()
+    .AddApplicationPart(typeof(TestController).Assembly);
+builder.Services.AddOpenApi();
+
+var app = builder.Build();
+
+app.MapControllers();
+
+app.Run();
+
+[ApiController]
+[Route("[controller]")]
+public class TestController : ControllerBase
+{
+    /// <param name="userId">The id of the user.</param>
+    [HttpGet("{user_id}")]
+    public string Get([FromRoute(Name = "user_id")] int userId)
+    {
+        return "Hello, World!";
+    }
+
+    [HttpGet]
+    public IEnumerable<Person> Search(Query query)
+    {
+        return [];
+    }
+}
+
+public partial class Program {}
+
+public record Person(int Id, string Name);
+
+public class Query
+{
+    /// <summary>
+    /// The full name of the person.
+    /// </summary>
+    [FromQuery(Name = "full_name")]
+    public string? Name { get; init; }
+}
+""";
+        var generator = new XmlCommentGenerator();
+        await SnapshotTestHelper.Verify(source, generator, out var compilation);
+        await SnapshotTestHelper.VerifyOpenApi(compilation, document =>
+        {
+            var getOperation = document.Paths["/Test/{user_id}"].Operations[HttpMethod.Get];
+            Assert.Equal("user_id", getOperation.Parameters[0].Name);
+            Assert.Equal("The id of the user.", getOperation.Parameters[0].Description);
+
+            var searchOperation = document.Paths["/Test"].Operations[HttpMethod.Get];
+            Assert.Equal("full_name", searchOperation.Parameters[0].Name);
+            Assert.Equal("The full name of the person.", searchOperation.Parameters[0].Description);
+        });
+    }
+
+    [Fact]
+    public async Task ShouldNotApplyCancellationTokenDocumentationToRequestBody()
+    {
+        var source =
+"""
+using System.Collections.Generic;
+using System.Threading;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.DependencyInjection;
+
+var builder = WebApplication.CreateBuilder();
+
+builder.Services
+    .AddControllers()
+    .AddApplicationPart(typeof(TestController).Assembly);
+builder.Services.AddOpenApi();
+
+var app = builder.Build();
+
+app.MapControllers();
+
+app.Run();
+
+[ApiController]
+[Route("[controller]")]
+public class TestController : ControllerBase
+{
+    /// <param name="cancellationToken">The cancellation token.</param>
+    [HttpGet]
+    public ActionResult Create(Person person, CancellationToken cancellationToken)
+    {
+        return Created();
+    }
+}
+
+public partial class Program {}
+
+public record Person(int Id, string Name);
+""";
+        var generator = new XmlCommentGenerator();
+        await SnapshotTestHelper.Verify(source, generator, out var compilation);
+        await SnapshotTestHelper.VerifyOpenApi(compilation, document =>
+        {
+            var getOperation = document.Paths["/Test"].Operations[HttpMethod.Get];
+            Assert.Null(getOperation.RequestBody.Description);
+        });
+    }
+
+    [Fact]
+    public async Task ShouldNotApplyFromServicesDocumentationToRequestBody()
+    {
+        var source =
+"""
+using System.Collections.Generic;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Mvc;
+using Microsoft.Extensions.DependencyInjection;
+
+var builder = WebApplication.CreateBuilder();
+
+builder.Services
+    .AddControllers()
+    .AddApplicationPart(typeof(TestController).Assembly);
+builder.Services.AddOpenApi();
+
+var app = builder.Build();
+
+app.MapControllers();
+
+app.Run();
+
+[ApiController]
+[Route("[controller]")]
+public class TestController : ControllerBase
+{
+    /// <param name="service">The service used to create the resource.</param>
+    [HttpGet]
+    public ActionResult Create(Person person, [FromServices] ITestService service)
+    {
+        return Created();
+    }
+}
+
+public interface ITestService {}
+
+public partial class Program {}
+
+public record Person(int Id, string Name);
+""";
+        var generator = new XmlCommentGenerator();
+        await SnapshotTestHelper.Verify(source, generator, out var compilation);
+        await SnapshotTestHelper.VerifyOpenApi(compilation, document =>
+        {
+            var getOperation = document.Paths["/Test"].Operations[HttpMethod.Get];
+            // The `service` parameter is bound from DI, not the request body, so its
+            // documentation must not be applied to the request body description.
+            Assert.Null(getOperation.RequestBody.Description);
+        });
+    }
 }
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/OperationTests.MinimalApis.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/OperationTests.MinimalApis.cs
index dad4380e2f9a..c3cb8044c397 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/OperationTests.MinimalApis.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/OperationTests.MinimalApis.cs
@@ -239,7 +239,7 @@ public static IResult Post19(string regularParam, [AsParameters] MixedParameters
     /// <param name="bindingParams">Parameters from different sources.</param>
     public static IResult Get20([AsParameters] BindingSourceParametersClass bindingParams)
     {
-        return TypedResults.Ok($"Query: {bindingParams.QueryParam}, Header: {bindingParams.HeaderParam}");
+        return TypedResults.Ok($"Query: {bindingParams.QueryParam}, Query with custom name: {bindingParams.QueryParamWithCustomName}, Header: {bindingParams.HeaderParam}");
     }
 
     /// <summary>
@@ -348,6 +348,12 @@ public class BindingSourceParametersClass
     [FromQuery]
     public string? QueryParam { get; set; }
 
+    /// <summary>
+    /// Query parameter from URL with custom name.
+    /// </summary>
+    [FromQuery(Name = "custom_name")]
+    public string? QueryParamWithCustomName { get; set; }
+
     /// <summary>
     /// Header value from request.
     /// </summary>
@@ -496,7 +502,10 @@ await SnapshotTestHelper.VerifyOpenApi(compilation, document =>
             var path20 = document.Paths["/20"].Operations[HttpMethod.Get];
             Assert.Equal("Tests AsParameters with different binding sources.", path20.Summary);
             Assert.Equal("Query parameter from URL.", path20.Parameters[0].Description);
-            Assert.Equal("Header value from request.", path20.Parameters[1].Description);
+            var customNameParam = path20.Parameters[1];
+            Assert.Equal("custom_name", customNameParam.Name);
+            Assert.Equal("Query parameter from URL with custom name.", customNameParam.Description);
+            Assert.Equal("Header value from request.", path20.Parameters[2].Description);
 
             // Test XML documentation priority order: value > returns > summary
             var path22 = document.Paths["/21"].Operations[HttpMethod.Get];
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/AddOpenApiTests.CanInterceptAddOpenApi#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/AddOpenApiTests.CanInterceptAddOpenApi#OpenApiXmlCommentSupport.generated.verified.cs
index 6c44a0094278..92baee2f72b2 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/AddOpenApiTests.CanInterceptAddOpenApi#OpenApiXmlCommentSupport.generated.verified.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/AddOpenApiTests.CanInterceptAddOpenApi#OpenApiXmlCommentSupport.generated.verified.cs
@@ -1,4 +1,4 @@
-//HintName: OpenApiXmlCommentSupport.generated.cs
+//HintName: OpenApiXmlCommentSupport.generated.cs
 //------------------------------------------------------------------------------
 // <auto-generated>
 //     This code was generated by a tool.
@@ -39,6 +39,7 @@ namespace Microsoft.AspNetCore.OpenApi.Generated
     using System.Threading.Tasks;
     using Microsoft.AspNetCore.OpenApi;
     using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
     using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
     using Microsoft.Extensions.DependencyInjection;
     using Microsoft.OpenApi;
@@ -135,30 +136,6 @@ public static string CreateDocumentationId(this PropertyInfo property)
             return sb.ToString();
         }
 
-        /// <summary>
-        /// Generates a documentation comment ID for a property given its container type and property name.
-        /// Example: P:Namespace.ContainingType.PropertyName
-        /// </summary>
-        public static string CreateDocumentationId(Type containerType, string propertyName)
-        {
-            if (containerType == null)
-            {
-                throw new ArgumentNullException(nameof(containerType));
-            }
-            if (string.IsNullOrEmpty(propertyName))
-            {
-                throw new ArgumentException("Property name cannot be null or empty.", nameof(propertyName));
-            }
-
-            var sb = new StringBuilder();
-            sb.Append("P:");
-            sb.Append(GetTypeDocId(containerType, includeGenericArguments: false, omitGenericArity: false));
-            sb.Append('.');
-            sb.Append(propertyName);
-
-            return sb.ToString();
-        }
-
         /// <summary>
         /// Generates a documentation comment ID for a method (or constructor).
         /// For example:
@@ -371,7 +348,7 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     foreach (var parameterComment in methodComment.Parameters)
                     {
                         var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
-                        var operationParameter = operation.Parameters?.SingleOrDefault(parameter => parameter.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
                         if (operationParameter is not null)
                         {
                             var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
@@ -382,7 +359,10 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                             }
                             targetOperationParameter.Deprecated = parameterComment.Deprecated;
                         }
-                        else
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
                         {
                             var requestBody = operation.RequestBody;
                             if (requestBody is not null)
@@ -431,10 +411,14 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     && metadata.ContainerType is { } containerType
                     && metadata.PropertyName is { } propertyName)
                 {
-                    var propertyDocId = DocumentationCommentIdHelper.CreateDocumentationId(containerType, propertyName);
-                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyDocId), out var propertyComment))
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
                     {
-                        var parameter = operation.Parameters?.SingleOrDefault(p => p.Name == metadata.Name);
+                        var parameter = GetOperationParameter(operation, propertyInfo);
                         var description = propertyComment.Summary;
                         if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
                         {
@@ -481,6 +465,86 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
             return Task.CompletedTask;
         }
 
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
         private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
         {
             if (sourceParameter is OpenApiParameterReference parameterReference)
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/AdditionalTextsTests.CanHandleXmlForSchemasInAdditionalTexts#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/AdditionalTextsTests.CanHandleXmlForSchemasInAdditionalTexts#OpenApiXmlCommentSupport.generated.verified.cs
index 0e41890976c0..321a982b076b 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/AdditionalTextsTests.CanHandleXmlForSchemasInAdditionalTexts#OpenApiXmlCommentSupport.generated.verified.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/AdditionalTextsTests.CanHandleXmlForSchemasInAdditionalTexts#OpenApiXmlCommentSupport.generated.verified.cs
@@ -1,4 +1,4 @@
-//HintName: OpenApiXmlCommentSupport.generated.cs
+//HintName: OpenApiXmlCommentSupport.generated.cs
 //------------------------------------------------------------------------------
 // <auto-generated>
 //     This code was generated by a tool.
@@ -39,6 +39,7 @@ namespace Microsoft.AspNetCore.OpenApi.Generated
     using System.Threading.Tasks;
     using Microsoft.AspNetCore.OpenApi;
     using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
     using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
     using Microsoft.Extensions.DependencyInjection;
     using Microsoft.OpenApi;
@@ -164,30 +165,6 @@ public static string CreateDocumentationId(this PropertyInfo property)
             return sb.ToString();
         }
 
-        /// <summary>
-        /// Generates a documentation comment ID for a property given its container type and property name.
-        /// Example: P:Namespace.ContainingType.PropertyName
-        /// </summary>
-        public static string CreateDocumentationId(Type containerType, string propertyName)
-        {
-            if (containerType == null)
-            {
-                throw new ArgumentNullException(nameof(containerType));
-            }
-            if (string.IsNullOrEmpty(propertyName))
-            {
-                throw new ArgumentException("Property name cannot be null or empty.", nameof(propertyName));
-            }
-
-            var sb = new StringBuilder();
-            sb.Append("P:");
-            sb.Append(GetTypeDocId(containerType, includeGenericArguments: false, omitGenericArity: false));
-            sb.Append('.');
-            sb.Append(propertyName);
-
-            return sb.ToString();
-        }
-
         /// <summary>
         /// Generates a documentation comment ID for a method (or constructor).
         /// For example:
@@ -400,7 +377,7 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     foreach (var parameterComment in methodComment.Parameters)
                     {
                         var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
-                        var operationParameter = operation.Parameters?.SingleOrDefault(parameter => parameter.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
                         if (operationParameter is not null)
                         {
                             var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
@@ -411,7 +388,10 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                             }
                             targetOperationParameter.Deprecated = parameterComment.Deprecated;
                         }
-                        else
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
                         {
                             var requestBody = operation.RequestBody;
                             if (requestBody is not null)
@@ -460,10 +440,14 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     && metadata.ContainerType is { } containerType
                     && metadata.PropertyName is { } propertyName)
                 {
-                    var propertyDocId = DocumentationCommentIdHelper.CreateDocumentationId(containerType, propertyName);
-                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyDocId), out var propertyComment))
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
                     {
-                        var parameter = operation.Parameters?.SingleOrDefault(p => p.Name == metadata.Name);
+                        var parameter = GetOperationParameter(operation, propertyInfo);
                         var description = propertyComment.Summary;
                         if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
                         {
@@ -510,6 +494,86 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
             return Task.CompletedTask;
         }
 
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
         private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
         {
             if (sourceParameter is OpenApiParameterReference parameterReference)
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/CompletenessTests.SupportsAllXmlTagsOnSchemas#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/CompletenessTests.SupportsAllXmlTagsOnSchemas#OpenApiXmlCommentSupport.generated.verified.cs
index 4a0aaf7895bf..96e654bce6b0 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/CompletenessTests.SupportsAllXmlTagsOnSchemas#OpenApiXmlCommentSupport.generated.verified.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/CompletenessTests.SupportsAllXmlTagsOnSchemas#OpenApiXmlCommentSupport.generated.verified.cs
@@ -1,4 +1,4 @@
-//HintName: OpenApiXmlCommentSupport.generated.cs
+//HintName: OpenApiXmlCommentSupport.generated.cs
 //------------------------------------------------------------------------------
 // <auto-generated>
 //     This code was generated by a tool.
@@ -39,6 +39,7 @@ namespace Microsoft.AspNetCore.OpenApi.Generated
     using System.Threading.Tasks;
     using Microsoft.AspNetCore.OpenApi;
     using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
     using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
     using Microsoft.Extensions.DependencyInjection;
     using Microsoft.OpenApi;
@@ -262,30 +263,6 @@ public static string CreateDocumentationId(this PropertyInfo property)
             return sb.ToString();
         }
 
-        /// <summary>
-        /// Generates a documentation comment ID for a property given its container type and property name.
-        /// Example: P:Namespace.ContainingType.PropertyName
-        /// </summary>
-        public static string CreateDocumentationId(Type containerType, string propertyName)
-        {
-            if (containerType == null)
-            {
-                throw new ArgumentNullException(nameof(containerType));
-            }
-            if (string.IsNullOrEmpty(propertyName))
-            {
-                throw new ArgumentException("Property name cannot be null or empty.", nameof(propertyName));
-            }
-
-            var sb = new StringBuilder();
-            sb.Append("P:");
-            sb.Append(GetTypeDocId(containerType, includeGenericArguments: false, omitGenericArity: false));
-            sb.Append('.');
-            sb.Append(propertyName);
-
-            return sb.ToString();
-        }
-
         /// <summary>
         /// Generates a documentation comment ID for a method (or constructor).
         /// For example:
@@ -498,7 +475,7 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     foreach (var parameterComment in methodComment.Parameters)
                     {
                         var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
-                        var operationParameter = operation.Parameters?.SingleOrDefault(parameter => parameter.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
                         if (operationParameter is not null)
                         {
                             var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
@@ -509,7 +486,10 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                             }
                             targetOperationParameter.Deprecated = parameterComment.Deprecated;
                         }
-                        else
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
                         {
                             var requestBody = operation.RequestBody;
                             if (requestBody is not null)
@@ -558,10 +538,14 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     && metadata.ContainerType is { } containerType
                     && metadata.PropertyName is { } propertyName)
                 {
-                    var propertyDocId = DocumentationCommentIdHelper.CreateDocumentationId(containerType, propertyName);
-                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyDocId), out var propertyComment))
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
                     {
-                        var parameter = operation.Parameters?.SingleOrDefault(p => p.Name == metadata.Name);
+                        var parameter = GetOperationParameter(operation, propertyInfo);
                         var description = propertyComment.Summary;
                         if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
                         {
@@ -608,6 +592,86 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
             return Task.CompletedTask;
         }
 
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
         private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
         {
             if (sourceParameter is OpenApiParameterReference parameterReference)
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.ShouldNotApplyCancellationTokenDocumentationToRequestBody#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.ShouldNotApplyCancellationTokenDocumentationToRequestBody#OpenApiXmlCommentSupport.generated.verified.cs
new file mode 100644
index 000000000000..1759f8915bc6
--- /dev/null
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.ShouldNotApplyCancellationTokenDocumentationToRequestBody#OpenApiXmlCommentSupport.generated.verified.cs
@@ -0,0 +1,674 @@
+//HintName: OpenApiXmlCommentSupport.generated.cs
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by a tool.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+#nullable enable
+// Suppress warnings about obsolete types and members
+// in generated code
+#pragma warning disable CS0612, CS0618
+
+namespace System.Runtime.CompilerServices
+{
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
+    file sealed class InterceptsLocationAttribute : System.Attribute
+    {
+        public InterceptsLocationAttribute(int version, string data)
+        {
+        }
+    }
+}
+
+namespace Microsoft.AspNetCore.OpenApi.Generated
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics.CodeAnalysis;
+    using System.Globalization;
+    using System.Linq;
+    using System.Reflection;
+    using System.Text;
+    using System.Text.Json;
+    using System.Text.Json.Nodes;
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.OpenApi;
+    using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
+    using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
+    using Microsoft.Extensions.DependencyInjection;
+    using Microsoft.OpenApi;
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file record XmlComment(
+        string? Summary,
+        string? Description,
+        string? Remarks,
+        string? Returns,
+        string? Value,
+        bool Deprecated,
+        List<string>? Examples,
+        List<XmlParameterComment>? Parameters,
+        List<XmlResponseComment>? Responses);
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file record XmlParameterComment(string? Name, string? Description, string? Example, bool Deprecated);
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file record XmlResponseComment(string Code, string? Description, string? Example);
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class XmlCommentCache
+    {
+        private static Dictionary<string, XmlComment>? _cache;
+        public static Dictionary<string, XmlComment> Cache => _cache ??= GenerateCacheEntries();
+
+        private static Dictionary<string, XmlComment> GenerateCacheEntries()
+        {
+            var cache = new Dictionary<string, XmlComment>();
+
+            cache.Add(@"M:TestController.Create(Person,System.Threading.CancellationToken)", new XmlComment(null, null, null, null, null, false, null, [new XmlParameterComment(@"cancellationToken", @"The cancellation token.", null, false)], null));
+
+            return cache;
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class DocumentationCommentIdHelper
+    {
+        /// <summary>
+        /// Generates a documentation comment ID for a type.
+        /// Example: T:Namespace.Outer+Inner`1 becomes T:Namespace.Outer.Inner`1
+        /// </summary>
+        public static string CreateDocumentationId(this Type type)
+        {
+            if (type == null)
+            {
+                throw new ArgumentNullException(nameof(type));
+            }
+
+            return "T:" + GetTypeDocId(type, includeGenericArguments: false, omitGenericArity: false);
+        }
+
+        /// <summary>
+        /// Generates a documentation comment ID for a property.
+        /// Example: P:Namespace.ContainingType.PropertyName or for an indexer P:Namespace.ContainingType.Item(System.Int32)
+        /// </summary>
+        public static string CreateDocumentationId(this PropertyInfo property)
+        {
+            if (property == null)
+            {
+                throw new ArgumentNullException(nameof(property));
+            }
+
+            var sb = new StringBuilder();
+            sb.Append("P:");
+
+            if (property.DeclaringType != null)
+            {
+                sb.Append(GetTypeDocId(property.DeclaringType, includeGenericArguments: false, omitGenericArity: false));
+            }
+
+            sb.Append('.');
+            sb.Append(property.Name);
+
+            // For indexers, include the parameter list.
+            var indexParams = property.GetIndexParameters();
+            if (indexParams.Length > 0)
+            {
+                sb.Append('(');
+                for (int i = 0; i < indexParams.Length; i++)
+                {
+                    if (i > 0)
+                    {
+                        sb.Append(',');
+                    }
+
+                    sb.Append(GetTypeDocId(indexParams[i].ParameterType, includeGenericArguments: true, omitGenericArity: false));
+                }
+                sb.Append(')');
+            }
+
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// Generates a documentation comment ID for a method (or constructor).
+        /// For example:
+        ///   M:Namespace.ContainingType.MethodName(ParamType1,ParamType2)~ReturnType
+        ///   M:Namespace.ContainingType.#ctor(ParamType)
+        /// </summary>
+        public static string CreateDocumentationId(this MethodInfo method)
+        {
+            if (method == null)
+            {
+                throw new ArgumentNullException(nameof(method));
+            }
+
+            var sb = new StringBuilder();
+            sb.Append("M:");
+
+            // Append the fully qualified name of the declaring type.
+            if (method.DeclaringType != null)
+            {
+                sb.Append(GetTypeDocId(method.DeclaringType, includeGenericArguments: false, omitGenericArity: false));
+            }
+
+            sb.Append('.');
+
+            // Append the method name, handling constructors specially.
+            if (method.IsConstructor)
+            {
+                sb.Append(method.IsStatic ? "#cctor" : "#ctor");
+            }
+            else
+            {
+                sb.Append(method.Name);
+                if (method.IsGenericMethod)
+                {
+                    sb.Append("``");
+                    sb.AppendFormat(CultureInfo.InvariantCulture, "{0}", method.GetGenericArguments().Length);
+                }
+            }
+
+            // Append the parameter list, if any.
+            var parameters = method.GetParameters();
+            if (parameters.Length > 0)
+            {
+                sb.Append('(');
+                for (int i = 0; i < parameters.Length; i++)
+                {
+                    if (i > 0)
+                    {
+                        sb.Append(',');
+                    }
+
+                    // Omit the generic arity for the parameter type.
+                    sb.Append(GetTypeDocId(parameters[i].ParameterType, includeGenericArguments: true, omitGenericArity: true));
+                }
+                sb.Append(')');
+            }
+
+            // Append the return type after a '~' (if the method returns a value).
+            if (method.ReturnType != typeof(void))
+            {
+                sb.Append('~');
+                // Omit the generic arity for the return type.
+                sb.Append(GetTypeDocId(method.ReturnType, includeGenericArguments: true, omitGenericArity: true));
+            }
+
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// Generates a documentation ID string for a type.
+        /// This method handles nested types (replacing '+' with '.'),
+        /// generic types, arrays, pointers, by-ref types, and generic parameters.
+        /// The <paramref name="includeGenericArguments"/> flag controls whether
+        /// constructed generic type arguments are emitted, while <paramref name="omitGenericArity"/>
+        /// controls whether the generic arity marker (e.g. "`1") is appended.
+        /// </summary>
+        private static string GetTypeDocId(Type type, bool includeGenericArguments, bool omitGenericArity)
+        {
+            if (type.IsGenericParameter)
+            {
+                // Use `` for method-level generic parameters and ` for type-level.
+                if (type.DeclaringMethod != null)
+                {
+                    return "``" + type.GenericParameterPosition;
+                }
+                else if (type.DeclaringType != null)
+                {
+                    return "`" + type.GenericParameterPosition;
+                }
+                else
+                {
+                    return type.Name;
+                }
+            }
+
+            if (type.IsGenericType)
+            {
+                Type genericDef = type.GetGenericTypeDefinition();
+                string fullName = genericDef.FullName ?? genericDef.Name;
+
+                var sb = new StringBuilder(fullName.Length);
+
+                // Replace '+' with '.' for nested types
+                for (var i = 0; i < fullName.Length; i++)
+                {
+                    char c = fullName[i];
+                    if (c == '+')
+                    {
+                        sb.Append('.');
+                    }
+                    else if (c == '`')
+                    {
+                        break;
+                    }
+                    else
+                    {
+                        sb.Append(c);
+                    }
+                }
+
+                if (!omitGenericArity)
+                {
+                    int arity = genericDef.GetGenericArguments().Length;
+                    sb.Append('`');
+                    sb.AppendFormat(CultureInfo.InvariantCulture, "{0}", arity);
+                }
+
+                if (includeGenericArguments && !type.IsGenericTypeDefinition)
+                {
+                    var typeArgs = type.GetGenericArguments();
+                    sb.Append('{');
+
+                    for (int i = 0; i < typeArgs.Length; i++)
+                    {
+                        if (i > 0)
+                        {
+                            sb.Append(',');
+                        }
+
+                        sb.Append(GetTypeDocId(typeArgs[i], includeGenericArguments, omitGenericArity));
+                    }
+
+                    sb.Append('}');
+                }
+
+                return sb.ToString();
+            }
+
+            // For non-generic types, use FullName (if available) and replace nested type separators.
+            return (type.FullName ?? type.Name).Replace('+', '.');
+        }
+
+        /// <summary>
+        /// Normalizes a documentation comment ID to match the compiler-style format.
+        /// Strips the return type suffix for ordinary methods but retains it for conversion operators.
+        /// </summary>
+        /// <param name="docId">The documentation comment ID to normalize.</param>
+        /// <returns>The normalized documentation comment ID.</returns>
+        public static string NormalizeDocId(string docId)
+        {
+            // Find the tilde character that indicates the return type suffix
+            var tildeIndex = docId.IndexOf('~');
+            if (tildeIndex == -1)
+            {
+                // No return type suffix, return as-is
+                return docId;
+            }
+
+            // Check if this is a conversion operator (op_Implicit or op_Explicit)
+            // For these operators, we need to keep the return type suffix
+            if (docId.Contains("op_Implicit") || docId.Contains("op_Explicit"))
+            {
+                return docId;
+            }
+
+            // For ordinary methods, strip the return type suffix
+            return docId.Substring(0, tildeIndex);
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file class XmlCommentOperationTransformer : IOpenApiOperationTransformer
+    {
+        public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransformerContext context, CancellationToken cancellationToken)
+        {
+            var methodInfo = context.Description.ActionDescriptor is ControllerActionDescriptor controllerActionDescriptor
+                ? controllerActionDescriptor.MethodInfo
+                : context.Description.ActionDescriptor.EndpointMetadata.OfType<MethodInfo>().SingleOrDefault();
+
+            if (methodInfo is null)
+            {
+                return Task.CompletedTask;
+            }
+            if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(methodInfo.CreateDocumentationId()), out var methodComment))
+            {
+                if (methodComment.Summary is { } summary)
+                {
+                    operation.Summary = summary;
+                }
+                if (methodComment.Description is { } description)
+                {
+                    operation.Description = description;
+                }
+                if (methodComment.Remarks is { } remarks)
+                {
+                    operation.Description = remarks;
+                }
+                if (methodComment.Parameters is { Count: > 0})
+                {
+                    foreach (var parameterComment in methodComment.Parameters)
+                    {
+                        var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
+                        if (operationParameter is not null)
+                        {
+                            var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
+                            targetOperationParameter.Description = parameterComment.Description;
+                            if (parameterComment.Example is { } jsonString)
+                            {
+                                targetOperationParameter.Example = jsonString.Parse();
+                            }
+                            targetOperationParameter.Deprecated = parameterComment.Deprecated;
+                        }
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
+                        {
+                            var requestBody = operation.RequestBody;
+                            if (requestBody is not null)
+                            {
+                                requestBody.Description = parameterComment.Description;
+                                if (parameterComment.Example is { } jsonString)
+                                {
+                                    var content = requestBody?.Content?.Values;
+                                    if (content is null)
+                                    {
+                                        continue;
+                                    }
+                                    foreach (var mediaType in content.OfType<OpenApiMediaType>())
+                                    {
+                                        mediaType.Example = jsonString.Parse();
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+                // Applies `<returns>` on XML comments for operation with single response value.
+                if (methodComment.Returns is { } returns && operation.Responses is { Count: 1 })
+                {
+                    var response = operation.Responses.First();
+                    response.Value.Description = returns;
+                }
+                // Applies `<response>` on XML comments for operation with multiple response values.
+                if (methodComment.Responses is { Count: > 0} && operation.Responses is { Count: > 0 })
+                {
+                    foreach (var response in operation.Responses)
+                    {
+                        var responseComment = methodComment.Responses.SingleOrDefault(xmlResponse => xmlResponse.Code == response.Key);
+                        if (responseComment is not null)
+                        {
+                            response.Value.Description = responseComment.Description;
+                        }
+                    }
+                }
+            }
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                var metadata = parameterDescription.ModelMetadata;
+                if (metadata is not null
+                    && metadata.MetadataKind == ModelMetadataKind.Property
+                    && metadata.ContainerType is { } containerType
+                    && metadata.PropertyName is { } propertyName)
+                {
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
+                    {
+                        var parameter = GetOperationParameter(operation, propertyInfo);
+                        var description = propertyComment.Summary;
+                        if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
+                        {
+                            description = $"{description}\n{propertyComment.Value}";
+                        }
+                        else if (string.IsNullOrEmpty(description))
+                        {
+                            description = propertyComment.Value;
+                        }
+                        if (parameter is null)
+                        {
+                            if (operation.RequestBody is not null)
+                            {
+                                operation.RequestBody.Description = description;
+                                if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                                {
+                                    var content = operation.RequestBody.Content?.Values;
+                                    if (content is null)
+                                    {
+                                        continue;
+                                    }
+                                    var parsedExample = jsonString.Parse();
+                                    foreach (var mediaType in content.OfType<OpenApiMediaType>())
+                                    {
+                                        mediaType.Example = parsedExample;
+                                    }
+                                }
+                            }
+                            continue;
+                        }
+                        var targetOperationParameter = UnwrapOpenApiParameter(parameter);
+                        if (targetOperationParameter is not null)
+                        {
+                            targetOperationParameter.Description = description;
+                            if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                            {
+                                targetOperationParameter.Example = jsonString.Parse();
+                            }
+                        }
+                    }
+                }
+            }
+
+            return Task.CompletedTask;
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
+        private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
+        {
+            if (sourceParameter is OpenApiParameterReference parameterReference)
+            {
+                if (parameterReference.Target is OpenApiParameter target)
+                {
+                    return target;
+                }
+                else
+                {
+                    throw new InvalidOperationException($"The input schema must be an {nameof(OpenApiParameter)} or {nameof(OpenApiParameterReference)}.");
+                }
+            }
+            else if (sourceParameter is OpenApiParameter directParameter)
+            {
+                return directParameter;
+            }
+            else
+            {
+                throw new InvalidOperationException($"The input schema must be an {nameof(OpenApiParameter)} or {nameof(OpenApiParameterReference)}.");
+            }
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file class XmlCommentSchemaTransformer : IOpenApiSchemaTransformer
+    {
+        public Task TransformAsync(OpenApiSchema schema, OpenApiSchemaTransformerContext context, CancellationToken cancellationToken)
+        {
+            // Apply comments from the type
+            if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(context.JsonTypeInfo.Type.CreateDocumentationId()), out var typeComment))
+            {
+                schema.Description = typeComment.Summary;
+                if (typeComment.Examples?.FirstOrDefault() is { } jsonString)
+                {
+                    schema.Example = jsonString.Parse();
+                }
+            }
+
+            if (context.JsonPropertyInfo is { AttributeProvider: PropertyInfo propertyInfo })
+            {
+                // Apply comments from the property
+                if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
+                {
+                    var description = propertyComment.Summary;
+                    if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
+                    {
+                        description = $"{description}\n{propertyComment.Value}";
+                    }
+                    else if (string.IsNullOrEmpty(description))
+                    {
+                        description = propertyComment.Value;
+                    }
+                    if (schema.Metadata is null
+                        || !schema.Metadata.TryGetValue("x-schema-id", out var schemaId)
+                        || string.IsNullOrEmpty(schemaId as string))
+                    {
+                        // Inlined schema
+                        schema.Description = description;
+                        if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                        {
+                            schema.Example = jsonString.Parse();
+                        }
+                    }
+                    else
+                    {
+                        // Schema Reference
+                        if (!string.IsNullOrEmpty(description))
+                        {
+                            schema.Metadata["x-ref-description"] = description;
+                        }
+                        if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                        {
+                            schema.Metadata["x-ref-example"] = jsonString.Parse()!;
+                        }
+                    }
+                }
+            }
+            return Task.CompletedTask;
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class JsonNodeExtensions
+    {
+        public static JsonNode? Parse(this string? json)
+        {
+            if (json is null)
+            {
+                return null;
+            }
+
+            try
+            {
+                return JsonNode.Parse(json);
+            }
+            catch (JsonException)
+            {
+                try
+                {
+                    // If parsing fails, try wrapping in quotes to make it a valid JSON string
+                    return JsonNode.Parse($"\"{json.Replace("\"", "\\\"")}\"");
+                }
+                catch (JsonException)
+                {
+                    return null;
+                }
+            }
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class GeneratedServiceCollectionExtensions
+    {
+        [InterceptsLocation]
+        public static IServiceCollection AddOpenApi(this IServiceCollection services)
+        {
+            return services.AddOpenApi("v1", options =>
+            {
+                options.AddSchemaTransformer(new XmlCommentSchemaTransformer());
+                options.AddOperationTransformer(new XmlCommentOperationTransformer());
+            });
+        }
+
+    }
+}
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.ShouldNotApplyFromServicesDocumentationToRequestBody#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.ShouldNotApplyFromServicesDocumentationToRequestBody#OpenApiXmlCommentSupport.generated.verified.cs
new file mode 100644
index 000000000000..298b174fa328
--- /dev/null
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.ShouldNotApplyFromServicesDocumentationToRequestBody#OpenApiXmlCommentSupport.generated.verified.cs
@@ -0,0 +1,674 @@
+//HintName: OpenApiXmlCommentSupport.generated.cs
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by a tool.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+#nullable enable
+// Suppress warnings about obsolete types and members
+// in generated code
+#pragma warning disable CS0612, CS0618
+
+namespace System.Runtime.CompilerServices
+{
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
+    file sealed class InterceptsLocationAttribute : System.Attribute
+    {
+        public InterceptsLocationAttribute(int version, string data)
+        {
+        }
+    }
+}
+
+namespace Microsoft.AspNetCore.OpenApi.Generated
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics.CodeAnalysis;
+    using System.Globalization;
+    using System.Linq;
+    using System.Reflection;
+    using System.Text;
+    using System.Text.Json;
+    using System.Text.Json.Nodes;
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.OpenApi;
+    using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
+    using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
+    using Microsoft.Extensions.DependencyInjection;
+    using Microsoft.OpenApi;
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file record XmlComment(
+        string? Summary,
+        string? Description,
+        string? Remarks,
+        string? Returns,
+        string? Value,
+        bool Deprecated,
+        List<string>? Examples,
+        List<XmlParameterComment>? Parameters,
+        List<XmlResponseComment>? Responses);
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file record XmlParameterComment(string? Name, string? Description, string? Example, bool Deprecated);
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file record XmlResponseComment(string Code, string? Description, string? Example);
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class XmlCommentCache
+    {
+        private static Dictionary<string, XmlComment>? _cache;
+        public static Dictionary<string, XmlComment> Cache => _cache ??= GenerateCacheEntries();
+
+        private static Dictionary<string, XmlComment> GenerateCacheEntries()
+        {
+            var cache = new Dictionary<string, XmlComment>();
+
+            cache.Add(@"M:TestController.Create(Person,ITestService)", new XmlComment(null, null, null, null, null, false, null, [new XmlParameterComment(@"service", @"The service used to create the resource.", null, false)], null));
+
+            return cache;
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class DocumentationCommentIdHelper
+    {
+        /// <summary>
+        /// Generates a documentation comment ID for a type.
+        /// Example: T:Namespace.Outer+Inner`1 becomes T:Namespace.Outer.Inner`1
+        /// </summary>
+        public static string CreateDocumentationId(this Type type)
+        {
+            if (type == null)
+            {
+                throw new ArgumentNullException(nameof(type));
+            }
+
+            return "T:" + GetTypeDocId(type, includeGenericArguments: false, omitGenericArity: false);
+        }
+
+        /// <summary>
+        /// Generates a documentation comment ID for a property.
+        /// Example: P:Namespace.ContainingType.PropertyName or for an indexer P:Namespace.ContainingType.Item(System.Int32)
+        /// </summary>
+        public static string CreateDocumentationId(this PropertyInfo property)
+        {
+            if (property == null)
+            {
+                throw new ArgumentNullException(nameof(property));
+            }
+
+            var sb = new StringBuilder();
+            sb.Append("P:");
+
+            if (property.DeclaringType != null)
+            {
+                sb.Append(GetTypeDocId(property.DeclaringType, includeGenericArguments: false, omitGenericArity: false));
+            }
+
+            sb.Append('.');
+            sb.Append(property.Name);
+
+            // For indexers, include the parameter list.
+            var indexParams = property.GetIndexParameters();
+            if (indexParams.Length > 0)
+            {
+                sb.Append('(');
+                for (int i = 0; i < indexParams.Length; i++)
+                {
+                    if (i > 0)
+                    {
+                        sb.Append(',');
+                    }
+
+                    sb.Append(GetTypeDocId(indexParams[i].ParameterType, includeGenericArguments: true, omitGenericArity: false));
+                }
+                sb.Append(')');
+            }
+
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// Generates a documentation comment ID for a method (or constructor).
+        /// For example:
+        ///   M:Namespace.ContainingType.MethodName(ParamType1,ParamType2)~ReturnType
+        ///   M:Namespace.ContainingType.#ctor(ParamType)
+        /// </summary>
+        public static string CreateDocumentationId(this MethodInfo method)
+        {
+            if (method == null)
+            {
+                throw new ArgumentNullException(nameof(method));
+            }
+
+            var sb = new StringBuilder();
+            sb.Append("M:");
+
+            // Append the fully qualified name of the declaring type.
+            if (method.DeclaringType != null)
+            {
+                sb.Append(GetTypeDocId(method.DeclaringType, includeGenericArguments: false, omitGenericArity: false));
+            }
+
+            sb.Append('.');
+
+            // Append the method name, handling constructors specially.
+            if (method.IsConstructor)
+            {
+                sb.Append(method.IsStatic ? "#cctor" : "#ctor");
+            }
+            else
+            {
+                sb.Append(method.Name);
+                if (method.IsGenericMethod)
+                {
+                    sb.Append("``");
+                    sb.AppendFormat(CultureInfo.InvariantCulture, "{0}", method.GetGenericArguments().Length);
+                }
+            }
+
+            // Append the parameter list, if any.
+            var parameters = method.GetParameters();
+            if (parameters.Length > 0)
+            {
+                sb.Append('(');
+                for (int i = 0; i < parameters.Length; i++)
+                {
+                    if (i > 0)
+                    {
+                        sb.Append(',');
+                    }
+
+                    // Omit the generic arity for the parameter type.
+                    sb.Append(GetTypeDocId(parameters[i].ParameterType, includeGenericArguments: true, omitGenericArity: true));
+                }
+                sb.Append(')');
+            }
+
+            // Append the return type after a '~' (if the method returns a value).
+            if (method.ReturnType != typeof(void))
+            {
+                sb.Append('~');
+                // Omit the generic arity for the return type.
+                sb.Append(GetTypeDocId(method.ReturnType, includeGenericArguments: true, omitGenericArity: true));
+            }
+
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// Generates a documentation ID string for a type.
+        /// This method handles nested types (replacing '+' with '.'),
+        /// generic types, arrays, pointers, by-ref types, and generic parameters.
+        /// The <paramref name="includeGenericArguments"/> flag controls whether
+        /// constructed generic type arguments are emitted, while <paramref name="omitGenericArity"/>
+        /// controls whether the generic arity marker (e.g. "`1") is appended.
+        /// </summary>
+        private static string GetTypeDocId(Type type, bool includeGenericArguments, bool omitGenericArity)
+        {
+            if (type.IsGenericParameter)
+            {
+                // Use `` for method-level generic parameters and ` for type-level.
+                if (type.DeclaringMethod != null)
+                {
+                    return "``" + type.GenericParameterPosition;
+                }
+                else if (type.DeclaringType != null)
+                {
+                    return "`" + type.GenericParameterPosition;
+                }
+                else
+                {
+                    return type.Name;
+                }
+            }
+
+            if (type.IsGenericType)
+            {
+                Type genericDef = type.GetGenericTypeDefinition();
+                string fullName = genericDef.FullName ?? genericDef.Name;
+
+                var sb = new StringBuilder(fullName.Length);
+
+                // Replace '+' with '.' for nested types
+                for (var i = 0; i < fullName.Length; i++)
+                {
+                    char c = fullName[i];
+                    if (c == '+')
+                    {
+                        sb.Append('.');
+                    }
+                    else if (c == '`')
+                    {
+                        break;
+                    }
+                    else
+                    {
+                        sb.Append(c);
+                    }
+                }
+
+                if (!omitGenericArity)
+                {
+                    int arity = genericDef.GetGenericArguments().Length;
+                    sb.Append('`');
+                    sb.AppendFormat(CultureInfo.InvariantCulture, "{0}", arity);
+                }
+
+                if (includeGenericArguments && !type.IsGenericTypeDefinition)
+                {
+                    var typeArgs = type.GetGenericArguments();
+                    sb.Append('{');
+
+                    for (int i = 0; i < typeArgs.Length; i++)
+                    {
+                        if (i > 0)
+                        {
+                            sb.Append(',');
+                        }
+
+                        sb.Append(GetTypeDocId(typeArgs[i], includeGenericArguments, omitGenericArity));
+                    }
+
+                    sb.Append('}');
+                }
+
+                return sb.ToString();
+            }
+
+            // For non-generic types, use FullName (if available) and replace nested type separators.
+            return (type.FullName ?? type.Name).Replace('+', '.');
+        }
+
+        /// <summary>
+        /// Normalizes a documentation comment ID to match the compiler-style format.
+        /// Strips the return type suffix for ordinary methods but retains it for conversion operators.
+        /// </summary>
+        /// <param name="docId">The documentation comment ID to normalize.</param>
+        /// <returns>The normalized documentation comment ID.</returns>
+        public static string NormalizeDocId(string docId)
+        {
+            // Find the tilde character that indicates the return type suffix
+            var tildeIndex = docId.IndexOf('~');
+            if (tildeIndex == -1)
+            {
+                // No return type suffix, return as-is
+                return docId;
+            }
+
+            // Check if this is a conversion operator (op_Implicit or op_Explicit)
+            // For these operators, we need to keep the return type suffix
+            if (docId.Contains("op_Implicit") || docId.Contains("op_Explicit"))
+            {
+                return docId;
+            }
+
+            // For ordinary methods, strip the return type suffix
+            return docId.Substring(0, tildeIndex);
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file class XmlCommentOperationTransformer : IOpenApiOperationTransformer
+    {
+        public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransformerContext context, CancellationToken cancellationToken)
+        {
+            var methodInfo = context.Description.ActionDescriptor is ControllerActionDescriptor controllerActionDescriptor
+                ? controllerActionDescriptor.MethodInfo
+                : context.Description.ActionDescriptor.EndpointMetadata.OfType<MethodInfo>().SingleOrDefault();
+
+            if (methodInfo is null)
+            {
+                return Task.CompletedTask;
+            }
+            if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(methodInfo.CreateDocumentationId()), out var methodComment))
+            {
+                if (methodComment.Summary is { } summary)
+                {
+                    operation.Summary = summary;
+                }
+                if (methodComment.Description is { } description)
+                {
+                    operation.Description = description;
+                }
+                if (methodComment.Remarks is { } remarks)
+                {
+                    operation.Description = remarks;
+                }
+                if (methodComment.Parameters is { Count: > 0})
+                {
+                    foreach (var parameterComment in methodComment.Parameters)
+                    {
+                        var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
+                        if (operationParameter is not null)
+                        {
+                            var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
+                            targetOperationParameter.Description = parameterComment.Description;
+                            if (parameterComment.Example is { } jsonString)
+                            {
+                                targetOperationParameter.Example = jsonString.Parse();
+                            }
+                            targetOperationParameter.Deprecated = parameterComment.Deprecated;
+                        }
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
+                        {
+                            var requestBody = operation.RequestBody;
+                            if (requestBody is not null)
+                            {
+                                requestBody.Description = parameterComment.Description;
+                                if (parameterComment.Example is { } jsonString)
+                                {
+                                    var content = requestBody?.Content?.Values;
+                                    if (content is null)
+                                    {
+                                        continue;
+                                    }
+                                    foreach (var mediaType in content.OfType<OpenApiMediaType>())
+                                    {
+                                        mediaType.Example = jsonString.Parse();
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+                // Applies `<returns>` on XML comments for operation with single response value.
+                if (methodComment.Returns is { } returns && operation.Responses is { Count: 1 })
+                {
+                    var response = operation.Responses.First();
+                    response.Value.Description = returns;
+                }
+                // Applies `<response>` on XML comments for operation with multiple response values.
+                if (methodComment.Responses is { Count: > 0} && operation.Responses is { Count: > 0 })
+                {
+                    foreach (var response in operation.Responses)
+                    {
+                        var responseComment = methodComment.Responses.SingleOrDefault(xmlResponse => xmlResponse.Code == response.Key);
+                        if (responseComment is not null)
+                        {
+                            response.Value.Description = responseComment.Description;
+                        }
+                    }
+                }
+            }
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                var metadata = parameterDescription.ModelMetadata;
+                if (metadata is not null
+                    && metadata.MetadataKind == ModelMetadataKind.Property
+                    && metadata.ContainerType is { } containerType
+                    && metadata.PropertyName is { } propertyName)
+                {
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
+                    {
+                        var parameter = GetOperationParameter(operation, propertyInfo);
+                        var description = propertyComment.Summary;
+                        if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
+                        {
+                            description = $"{description}\n{propertyComment.Value}";
+                        }
+                        else if (string.IsNullOrEmpty(description))
+                        {
+                            description = propertyComment.Value;
+                        }
+                        if (parameter is null)
+                        {
+                            if (operation.RequestBody is not null)
+                            {
+                                operation.RequestBody.Description = description;
+                                if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                                {
+                                    var content = operation.RequestBody.Content?.Values;
+                                    if (content is null)
+                                    {
+                                        continue;
+                                    }
+                                    var parsedExample = jsonString.Parse();
+                                    foreach (var mediaType in content.OfType<OpenApiMediaType>())
+                                    {
+                                        mediaType.Example = parsedExample;
+                                    }
+                                }
+                            }
+                            continue;
+                        }
+                        var targetOperationParameter = UnwrapOpenApiParameter(parameter);
+                        if (targetOperationParameter is not null)
+                        {
+                            targetOperationParameter.Description = description;
+                            if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                            {
+                                targetOperationParameter.Example = jsonString.Parse();
+                            }
+                        }
+                    }
+                }
+            }
+
+            return Task.CompletedTask;
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
+        private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
+        {
+            if (sourceParameter is OpenApiParameterReference parameterReference)
+            {
+                if (parameterReference.Target is OpenApiParameter target)
+                {
+                    return target;
+                }
+                else
+                {
+                    throw new InvalidOperationException($"The input schema must be an {nameof(OpenApiParameter)} or {nameof(OpenApiParameterReference)}.");
+                }
+            }
+            else if (sourceParameter is OpenApiParameter directParameter)
+            {
+                return directParameter;
+            }
+            else
+            {
+                throw new InvalidOperationException($"The input schema must be an {nameof(OpenApiParameter)} or {nameof(OpenApiParameterReference)}.");
+            }
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file class XmlCommentSchemaTransformer : IOpenApiSchemaTransformer
+    {
+        public Task TransformAsync(OpenApiSchema schema, OpenApiSchemaTransformerContext context, CancellationToken cancellationToken)
+        {
+            // Apply comments from the type
+            if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(context.JsonTypeInfo.Type.CreateDocumentationId()), out var typeComment))
+            {
+                schema.Description = typeComment.Summary;
+                if (typeComment.Examples?.FirstOrDefault() is { } jsonString)
+                {
+                    schema.Example = jsonString.Parse();
+                }
+            }
+
+            if (context.JsonPropertyInfo is { AttributeProvider: PropertyInfo propertyInfo })
+            {
+                // Apply comments from the property
+                if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
+                {
+                    var description = propertyComment.Summary;
+                    if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
+                    {
+                        description = $"{description}\n{propertyComment.Value}";
+                    }
+                    else if (string.IsNullOrEmpty(description))
+                    {
+                        description = propertyComment.Value;
+                    }
+                    if (schema.Metadata is null
+                        || !schema.Metadata.TryGetValue("x-schema-id", out var schemaId)
+                        || string.IsNullOrEmpty(schemaId as string))
+                    {
+                        // Inlined schema
+                        schema.Description = description;
+                        if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                        {
+                            schema.Example = jsonString.Parse();
+                        }
+                    }
+                    else
+                    {
+                        // Schema Reference
+                        if (!string.IsNullOrEmpty(description))
+                        {
+                            schema.Metadata["x-ref-description"] = description;
+                        }
+                        if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                        {
+                            schema.Metadata["x-ref-example"] = jsonString.Parse()!;
+                        }
+                    }
+                }
+            }
+            return Task.CompletedTask;
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class JsonNodeExtensions
+    {
+        public static JsonNode? Parse(this string? json)
+        {
+            if (json is null)
+            {
+                return null;
+            }
+
+            try
+            {
+                return JsonNode.Parse(json);
+            }
+            catch (JsonException)
+            {
+                try
+                {
+                    // If parsing fails, try wrapping in quotes to make it a valid JSON string
+                    return JsonNode.Parse($"\"{json.Replace("\"", "\\\"")}\"");
+                }
+                catch (JsonException)
+                {
+                    return null;
+                }
+            }
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class GeneratedServiceCollectionExtensions
+    {
+        [InterceptsLocation]
+        public static IServiceCollection AddOpenApi(this IServiceCollection services)
+        {
+            return services.AddOpenApi("v1", options =>
+            {
+                options.AddSchemaTransformer(new XmlCommentSchemaTransformer());
+                options.AddOperationTransformer(new XmlCommentOperationTransformer());
+            });
+        }
+
+    }
+}
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsParametersWithCustomNamesFromControllers#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsParametersWithCustomNamesFromControllers#OpenApiXmlCommentSupport.generated.verified.cs
new file mode 100644
index 000000000000..9b36137469fe
--- /dev/null
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsParametersWithCustomNamesFromControllers#OpenApiXmlCommentSupport.generated.verified.cs
@@ -0,0 +1,675 @@
+//HintName: OpenApiXmlCommentSupport.generated.cs
+//------------------------------------------------------------------------------
+// <auto-generated>
+//     This code was generated by a tool.
+//
+//     Changes to this file may cause incorrect behavior and will be lost if
+//     the code is regenerated.
+// </auto-generated>
+//------------------------------------------------------------------------------
+#nullable enable
+// Suppress warnings about obsolete types and members
+// in generated code
+#pragma warning disable CS0612, CS0618
+
+namespace System.Runtime.CompilerServices
+{
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    [AttributeUsage(AttributeTargets.Method, AllowMultiple = true)]
+    file sealed class InterceptsLocationAttribute : System.Attribute
+    {
+        public InterceptsLocationAttribute(int version, string data)
+        {
+        }
+    }
+}
+
+namespace Microsoft.AspNetCore.OpenApi.Generated
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics.CodeAnalysis;
+    using System.Globalization;
+    using System.Linq;
+    using System.Reflection;
+    using System.Text;
+    using System.Text.Json;
+    using System.Text.Json.Nodes;
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Microsoft.AspNetCore.OpenApi;
+    using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
+    using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
+    using Microsoft.Extensions.DependencyInjection;
+    using Microsoft.OpenApi;
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file record XmlComment(
+        string? Summary,
+        string? Description,
+        string? Remarks,
+        string? Returns,
+        string? Value,
+        bool Deprecated,
+        List<string>? Examples,
+        List<XmlParameterComment>? Parameters,
+        List<XmlResponseComment>? Responses);
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file record XmlParameterComment(string? Name, string? Description, string? Example, bool Deprecated);
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file record XmlResponseComment(string Code, string? Description, string? Example);
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class XmlCommentCache
+    {
+        private static Dictionary<string, XmlComment>? _cache;
+        public static Dictionary<string, XmlComment> Cache => _cache ??= GenerateCacheEntries();
+
+        private static Dictionary<string, XmlComment> GenerateCacheEntries()
+        {
+            var cache = new Dictionary<string, XmlComment>();
+
+            cache.Add(@"P:Query.Name", new XmlComment(@"The full name of the person.", null, null, null, null, false, null, null, null));
+            cache.Add(@"M:TestController.Get(System.Int32)", new XmlComment(null, null, null, null, null, false, null, [new XmlParameterComment(@"userId", @"The id of the user.", null, false)], null));
+
+            return cache;
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class DocumentationCommentIdHelper
+    {
+        /// <summary>
+        /// Generates a documentation comment ID for a type.
+        /// Example: T:Namespace.Outer+Inner`1 becomes T:Namespace.Outer.Inner`1
+        /// </summary>
+        public static string CreateDocumentationId(this Type type)
+        {
+            if (type == null)
+            {
+                throw new ArgumentNullException(nameof(type));
+            }
+
+            return "T:" + GetTypeDocId(type, includeGenericArguments: false, omitGenericArity: false);
+        }
+
+        /// <summary>
+        /// Generates a documentation comment ID for a property.
+        /// Example: P:Namespace.ContainingType.PropertyName or for an indexer P:Namespace.ContainingType.Item(System.Int32)
+        /// </summary>
+        public static string CreateDocumentationId(this PropertyInfo property)
+        {
+            if (property == null)
+            {
+                throw new ArgumentNullException(nameof(property));
+            }
+
+            var sb = new StringBuilder();
+            sb.Append("P:");
+
+            if (property.DeclaringType != null)
+            {
+                sb.Append(GetTypeDocId(property.DeclaringType, includeGenericArguments: false, omitGenericArity: false));
+            }
+
+            sb.Append('.');
+            sb.Append(property.Name);
+
+            // For indexers, include the parameter list.
+            var indexParams = property.GetIndexParameters();
+            if (indexParams.Length > 0)
+            {
+                sb.Append('(');
+                for (int i = 0; i < indexParams.Length; i++)
+                {
+                    if (i > 0)
+                    {
+                        sb.Append(',');
+                    }
+
+                    sb.Append(GetTypeDocId(indexParams[i].ParameterType, includeGenericArguments: true, omitGenericArity: false));
+                }
+                sb.Append(')');
+            }
+
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// Generates a documentation comment ID for a method (or constructor).
+        /// For example:
+        ///   M:Namespace.ContainingType.MethodName(ParamType1,ParamType2)~ReturnType
+        ///   M:Namespace.ContainingType.#ctor(ParamType)
+        /// </summary>
+        public static string CreateDocumentationId(this MethodInfo method)
+        {
+            if (method == null)
+            {
+                throw new ArgumentNullException(nameof(method));
+            }
+
+            var sb = new StringBuilder();
+            sb.Append("M:");
+
+            // Append the fully qualified name of the declaring type.
+            if (method.DeclaringType != null)
+            {
+                sb.Append(GetTypeDocId(method.DeclaringType, includeGenericArguments: false, omitGenericArity: false));
+            }
+
+            sb.Append('.');
+
+            // Append the method name, handling constructors specially.
+            if (method.IsConstructor)
+            {
+                sb.Append(method.IsStatic ? "#cctor" : "#ctor");
+            }
+            else
+            {
+                sb.Append(method.Name);
+                if (method.IsGenericMethod)
+                {
+                    sb.Append("``");
+                    sb.AppendFormat(CultureInfo.InvariantCulture, "{0}", method.GetGenericArguments().Length);
+                }
+            }
+
+            // Append the parameter list, if any.
+            var parameters = method.GetParameters();
+            if (parameters.Length > 0)
+            {
+                sb.Append('(');
+                for (int i = 0; i < parameters.Length; i++)
+                {
+                    if (i > 0)
+                    {
+                        sb.Append(',');
+                    }
+
+                    // Omit the generic arity for the parameter type.
+                    sb.Append(GetTypeDocId(parameters[i].ParameterType, includeGenericArguments: true, omitGenericArity: true));
+                }
+                sb.Append(')');
+            }
+
+            // Append the return type after a '~' (if the method returns a value).
+            if (method.ReturnType != typeof(void))
+            {
+                sb.Append('~');
+                // Omit the generic arity for the return type.
+                sb.Append(GetTypeDocId(method.ReturnType, includeGenericArguments: true, omitGenericArity: true));
+            }
+
+            return sb.ToString();
+        }
+
+        /// <summary>
+        /// Generates a documentation ID string for a type.
+        /// This method handles nested types (replacing '+' with '.'),
+        /// generic types, arrays, pointers, by-ref types, and generic parameters.
+        /// The <paramref name="includeGenericArguments"/> flag controls whether
+        /// constructed generic type arguments are emitted, while <paramref name="omitGenericArity"/>
+        /// controls whether the generic arity marker (e.g. "`1") is appended.
+        /// </summary>
+        private static string GetTypeDocId(Type type, bool includeGenericArguments, bool omitGenericArity)
+        {
+            if (type.IsGenericParameter)
+            {
+                // Use `` for method-level generic parameters and ` for type-level.
+                if (type.DeclaringMethod != null)
+                {
+                    return "``" + type.GenericParameterPosition;
+                }
+                else if (type.DeclaringType != null)
+                {
+                    return "`" + type.GenericParameterPosition;
+                }
+                else
+                {
+                    return type.Name;
+                }
+            }
+
+            if (type.IsGenericType)
+            {
+                Type genericDef = type.GetGenericTypeDefinition();
+                string fullName = genericDef.FullName ?? genericDef.Name;
+
+                var sb = new StringBuilder(fullName.Length);
+
+                // Replace '+' with '.' for nested types
+                for (var i = 0; i < fullName.Length; i++)
+                {
+                    char c = fullName[i];
+                    if (c == '+')
+                    {
+                        sb.Append('.');
+                    }
+                    else if (c == '`')
+                    {
+                        break;
+                    }
+                    else
+                    {
+                        sb.Append(c);
+                    }
+                }
+
+                if (!omitGenericArity)
+                {
+                    int arity = genericDef.GetGenericArguments().Length;
+                    sb.Append('`');
+                    sb.AppendFormat(CultureInfo.InvariantCulture, "{0}", arity);
+                }
+
+                if (includeGenericArguments && !type.IsGenericTypeDefinition)
+                {
+                    var typeArgs = type.GetGenericArguments();
+                    sb.Append('{');
+
+                    for (int i = 0; i < typeArgs.Length; i++)
+                    {
+                        if (i > 0)
+                        {
+                            sb.Append(',');
+                        }
+
+                        sb.Append(GetTypeDocId(typeArgs[i], includeGenericArguments, omitGenericArity));
+                    }
+
+                    sb.Append('}');
+                }
+
+                return sb.ToString();
+            }
+
+            // For non-generic types, use FullName (if available) and replace nested type separators.
+            return (type.FullName ?? type.Name).Replace('+', '.');
+        }
+
+        /// <summary>
+        /// Normalizes a documentation comment ID to match the compiler-style format.
+        /// Strips the return type suffix for ordinary methods but retains it for conversion operators.
+        /// </summary>
+        /// <param name="docId">The documentation comment ID to normalize.</param>
+        /// <returns>The normalized documentation comment ID.</returns>
+        public static string NormalizeDocId(string docId)
+        {
+            // Find the tilde character that indicates the return type suffix
+            var tildeIndex = docId.IndexOf('~');
+            if (tildeIndex == -1)
+            {
+                // No return type suffix, return as-is
+                return docId;
+            }
+
+            // Check if this is a conversion operator (op_Implicit or op_Explicit)
+            // For these operators, we need to keep the return type suffix
+            if (docId.Contains("op_Implicit") || docId.Contains("op_Explicit"))
+            {
+                return docId;
+            }
+
+            // For ordinary methods, strip the return type suffix
+            return docId.Substring(0, tildeIndex);
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file class XmlCommentOperationTransformer : IOpenApiOperationTransformer
+    {
+        public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransformerContext context, CancellationToken cancellationToken)
+        {
+            var methodInfo = context.Description.ActionDescriptor is ControllerActionDescriptor controllerActionDescriptor
+                ? controllerActionDescriptor.MethodInfo
+                : context.Description.ActionDescriptor.EndpointMetadata.OfType<MethodInfo>().SingleOrDefault();
+
+            if (methodInfo is null)
+            {
+                return Task.CompletedTask;
+            }
+            if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(methodInfo.CreateDocumentationId()), out var methodComment))
+            {
+                if (methodComment.Summary is { } summary)
+                {
+                    operation.Summary = summary;
+                }
+                if (methodComment.Description is { } description)
+                {
+                    operation.Description = description;
+                }
+                if (methodComment.Remarks is { } remarks)
+                {
+                    operation.Description = remarks;
+                }
+                if (methodComment.Parameters is { Count: > 0})
+                {
+                    foreach (var parameterComment in methodComment.Parameters)
+                    {
+                        var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
+                        if (operationParameter is not null)
+                        {
+                            var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
+                            targetOperationParameter.Description = parameterComment.Description;
+                            if (parameterComment.Example is { } jsonString)
+                            {
+                                targetOperationParameter.Example = jsonString.Parse();
+                            }
+                            targetOperationParameter.Deprecated = parameterComment.Deprecated;
+                        }
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
+                        {
+                            var requestBody = operation.RequestBody;
+                            if (requestBody is not null)
+                            {
+                                requestBody.Description = parameterComment.Description;
+                                if (parameterComment.Example is { } jsonString)
+                                {
+                                    var content = requestBody?.Content?.Values;
+                                    if (content is null)
+                                    {
+                                        continue;
+                                    }
+                                    foreach (var mediaType in content.OfType<OpenApiMediaType>())
+                                    {
+                                        mediaType.Example = jsonString.Parse();
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+                // Applies `<returns>` on XML comments for operation with single response value.
+                if (methodComment.Returns is { } returns && operation.Responses is { Count: 1 })
+                {
+                    var response = operation.Responses.First();
+                    response.Value.Description = returns;
+                }
+                // Applies `<response>` on XML comments for operation with multiple response values.
+                if (methodComment.Responses is { Count: > 0} && operation.Responses is { Count: > 0 })
+                {
+                    foreach (var response in operation.Responses)
+                    {
+                        var responseComment = methodComment.Responses.SingleOrDefault(xmlResponse => xmlResponse.Code == response.Key);
+                        if (responseComment is not null)
+                        {
+                            response.Value.Description = responseComment.Description;
+                        }
+                    }
+                }
+            }
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                var metadata = parameterDescription.ModelMetadata;
+                if (metadata is not null
+                    && metadata.MetadataKind == ModelMetadataKind.Property
+                    && metadata.ContainerType is { } containerType
+                    && metadata.PropertyName is { } propertyName)
+                {
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
+                    {
+                        var parameter = GetOperationParameter(operation, propertyInfo);
+                        var description = propertyComment.Summary;
+                        if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
+                        {
+                            description = $"{description}\n{propertyComment.Value}";
+                        }
+                        else if (string.IsNullOrEmpty(description))
+                        {
+                            description = propertyComment.Value;
+                        }
+                        if (parameter is null)
+                        {
+                            if (operation.RequestBody is not null)
+                            {
+                                operation.RequestBody.Description = description;
+                                if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                                {
+                                    var content = operation.RequestBody.Content?.Values;
+                                    if (content is null)
+                                    {
+                                        continue;
+                                    }
+                                    var parsedExample = jsonString.Parse();
+                                    foreach (var mediaType in content.OfType<OpenApiMediaType>())
+                                    {
+                                        mediaType.Example = parsedExample;
+                                    }
+                                }
+                            }
+                            continue;
+                        }
+                        var targetOperationParameter = UnwrapOpenApiParameter(parameter);
+                        if (targetOperationParameter is not null)
+                        {
+                            targetOperationParameter.Description = description;
+                            if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                            {
+                                targetOperationParameter.Example = jsonString.Parse();
+                            }
+                        }
+                    }
+                }
+            }
+
+            return Task.CompletedTask;
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
+        private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
+        {
+            if (sourceParameter is OpenApiParameterReference parameterReference)
+            {
+                if (parameterReference.Target is OpenApiParameter target)
+                {
+                    return target;
+                }
+                else
+                {
+                    throw new InvalidOperationException($"The input schema must be an {nameof(OpenApiParameter)} or {nameof(OpenApiParameterReference)}.");
+                }
+            }
+            else if (sourceParameter is OpenApiParameter directParameter)
+            {
+                return directParameter;
+            }
+            else
+            {
+                throw new InvalidOperationException($"The input schema must be an {nameof(OpenApiParameter)} or {nameof(OpenApiParameterReference)}.");
+            }
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file class XmlCommentSchemaTransformer : IOpenApiSchemaTransformer
+    {
+        public Task TransformAsync(OpenApiSchema schema, OpenApiSchemaTransformerContext context, CancellationToken cancellationToken)
+        {
+            // Apply comments from the type
+            if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(context.JsonTypeInfo.Type.CreateDocumentationId()), out var typeComment))
+            {
+                schema.Description = typeComment.Summary;
+                if (typeComment.Examples?.FirstOrDefault() is { } jsonString)
+                {
+                    schema.Example = jsonString.Parse();
+                }
+            }
+
+            if (context.JsonPropertyInfo is { AttributeProvider: PropertyInfo propertyInfo })
+            {
+                // Apply comments from the property
+                if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
+                {
+                    var description = propertyComment.Summary;
+                    if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
+                    {
+                        description = $"{description}\n{propertyComment.Value}";
+                    }
+                    else if (string.IsNullOrEmpty(description))
+                    {
+                        description = propertyComment.Value;
+                    }
+                    if (schema.Metadata is null
+                        || !schema.Metadata.TryGetValue("x-schema-id", out var schemaId)
+                        || string.IsNullOrEmpty(schemaId as string))
+                    {
+                        // Inlined schema
+                        schema.Description = description;
+                        if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                        {
+                            schema.Example = jsonString.Parse();
+                        }
+                    }
+                    else
+                    {
+                        // Schema Reference
+                        if (!string.IsNullOrEmpty(description))
+                        {
+                            schema.Metadata["x-ref-description"] = description;
+                        }
+                        if (propertyComment.Examples?.FirstOrDefault() is { } jsonString)
+                        {
+                            schema.Metadata["x-ref-example"] = jsonString.Parse()!;
+                        }
+                    }
+                }
+            }
+            return Task.CompletedTask;
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class JsonNodeExtensions
+    {
+        public static JsonNode? Parse(this string? json)
+        {
+            if (json is null)
+            {
+                return null;
+            }
+
+            try
+            {
+                return JsonNode.Parse(json);
+            }
+            catch (JsonException)
+            {
+                try
+                {
+                    // If parsing fails, try wrapping in quotes to make it a valid JSON string
+                    return JsonNode.Parse($"\"{json.Replace("\"", "\\\"")}\"");
+                }
+                catch (JsonException)
+                {
+                    return null;
+                }
+            }
+        }
+    }
+
+    [System.CodeDom.Compiler.GeneratedCodeAttribute("Microsoft.AspNetCore.OpenApi.SourceGenerators, Version=42.42.42.42, Culture=neutral, PublicKeyToken=adb9793829ddae60", "42.42.42.42")]
+    file static class GeneratedServiceCollectionExtensions
+    {
+        [InterceptsLocation]
+        public static IServiceCollection AddOpenApi(this IServiceCollection services)
+        {
+            return services.AddOpenApi("v1", options =>
+            {
+                options.AddSchemaTransformer(new XmlCommentSchemaTransformer());
+                options.AddOperationTransformer(new XmlCommentOperationTransformer());
+            });
+        }
+
+    }
+}
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsRouteParametersFromControllers#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsRouteParametersFromControllers#OpenApiXmlCommentSupport.generated.verified.cs
index e569ddc2f4a8..4d598388067d 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsRouteParametersFromControllers#OpenApiXmlCommentSupport.generated.verified.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsRouteParametersFromControllers#OpenApiXmlCommentSupport.generated.verified.cs
@@ -1,4 +1,4 @@
-//HintName: OpenApiXmlCommentSupport.generated.cs
+//HintName: OpenApiXmlCommentSupport.generated.cs
 //------------------------------------------------------------------------------
 // <auto-generated>
 //     This code was generated by a tool.
@@ -39,6 +39,7 @@ namespace Microsoft.AspNetCore.OpenApi.Generated
     using System.Threading.Tasks;
     using Microsoft.AspNetCore.OpenApi;
     using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
     using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
     using Microsoft.Extensions.DependencyInjection;
     using Microsoft.OpenApi;
@@ -136,30 +137,6 @@ public static string CreateDocumentationId(this PropertyInfo property)
             return sb.ToString();
         }
 
-        /// <summary>
-        /// Generates a documentation comment ID for a property given its container type and property name.
-        /// Example: P:Namespace.ContainingType.PropertyName
-        /// </summary>
-        public static string CreateDocumentationId(Type containerType, string propertyName)
-        {
-            if (containerType == null)
-            {
-                throw new ArgumentNullException(nameof(containerType));
-            }
-            if (string.IsNullOrEmpty(propertyName))
-            {
-                throw new ArgumentException("Property name cannot be null or empty.", nameof(propertyName));
-            }
-
-            var sb = new StringBuilder();
-            sb.Append("P:");
-            sb.Append(GetTypeDocId(containerType, includeGenericArguments: false, omitGenericArity: false));
-            sb.Append('.');
-            sb.Append(propertyName);
-
-            return sb.ToString();
-        }
-
         /// <summary>
         /// Generates a documentation comment ID for a method (or constructor).
         /// For example:
@@ -372,7 +349,7 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     foreach (var parameterComment in methodComment.Parameters)
                     {
                         var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
-                        var operationParameter = operation.Parameters?.SingleOrDefault(parameter => parameter.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
                         if (operationParameter is not null)
                         {
                             var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
@@ -383,7 +360,10 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                             }
                             targetOperationParameter.Deprecated = parameterComment.Deprecated;
                         }
-                        else
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
                         {
                             var requestBody = operation.RequestBody;
                             if (requestBody is not null)
@@ -432,10 +412,14 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     && metadata.ContainerType is { } containerType
                     && metadata.PropertyName is { } propertyName)
                 {
-                    var propertyDocId = DocumentationCommentIdHelper.CreateDocumentationId(containerType, propertyName);
-                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyDocId), out var propertyComment))
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
                     {
-                        var parameter = operation.Parameters?.SingleOrDefault(p => p.Name == metadata.Name);
+                        var parameter = GetOperationParameter(operation, propertyInfo);
                         var description = propertyComment.Summary;
                         if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
                         {
@@ -482,6 +466,86 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
             return Task.CompletedTask;
         }
 
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
         private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
         {
             if (sourceParameter is OpenApiParameterReference parameterReference)
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsXmlCommentsOnOperationsFromControllers#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsXmlCommentsOnOperationsFromControllers#OpenApiXmlCommentSupport.generated.verified.cs
index 6ac0fcb221a9..5d7d27ce3af8 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsXmlCommentsOnOperationsFromControllers#OpenApiXmlCommentSupport.generated.verified.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsXmlCommentsOnOperationsFromControllers#OpenApiXmlCommentSupport.generated.verified.cs
@@ -1,4 +1,4 @@
-//HintName: OpenApiXmlCommentSupport.generated.cs
+//HintName: OpenApiXmlCommentSupport.generated.cs
 //------------------------------------------------------------------------------
 // <auto-generated>
 //     This code was generated by a tool.
@@ -39,6 +39,7 @@ namespace Microsoft.AspNetCore.OpenApi.Generated
     using System.Threading.Tasks;
     using Microsoft.AspNetCore.OpenApi;
     using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
     using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
     using Microsoft.Extensions.DependencyInjection;
     using Microsoft.OpenApi;
@@ -139,30 +140,6 @@ public static string CreateDocumentationId(this PropertyInfo property)
             return sb.ToString();
         }
 
-        /// <summary>
-        /// Generates a documentation comment ID for a property given its container type and property name.
-        /// Example: P:Namespace.ContainingType.PropertyName
-        /// </summary>
-        public static string CreateDocumentationId(Type containerType, string propertyName)
-        {
-            if (containerType == null)
-            {
-                throw new ArgumentNullException(nameof(containerType));
-            }
-            if (string.IsNullOrEmpty(propertyName))
-            {
-                throw new ArgumentException("Property name cannot be null or empty.", nameof(propertyName));
-            }
-
-            var sb = new StringBuilder();
-            sb.Append("P:");
-            sb.Append(GetTypeDocId(containerType, includeGenericArguments: false, omitGenericArity: false));
-            sb.Append('.');
-            sb.Append(propertyName);
-
-            return sb.ToString();
-        }
-
         /// <summary>
         /// Generates a documentation comment ID for a method (or constructor).
         /// For example:
@@ -375,7 +352,7 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     foreach (var parameterComment in methodComment.Parameters)
                     {
                         var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
-                        var operationParameter = operation.Parameters?.SingleOrDefault(parameter => parameter.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
                         if (operationParameter is not null)
                         {
                             var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
@@ -386,7 +363,10 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                             }
                             targetOperationParameter.Deprecated = parameterComment.Deprecated;
                         }
-                        else
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
                         {
                             var requestBody = operation.RequestBody;
                             if (requestBody is not null)
@@ -435,10 +415,14 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     && metadata.ContainerType is { } containerType
                     && metadata.PropertyName is { } propertyName)
                 {
-                    var propertyDocId = DocumentationCommentIdHelper.CreateDocumentationId(containerType, propertyName);
-                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyDocId), out var propertyComment))
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
                     {
-                        var parameter = operation.Parameters?.SingleOrDefault(p => p.Name == metadata.Name);
+                        var parameter = GetOperationParameter(operation, propertyInfo);
                         var description = propertyComment.Summary;
                         if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
                         {
@@ -485,6 +469,86 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
             return Task.CompletedTask;
         }
 
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
         private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
         {
             if (sourceParameter is OpenApiParameterReference parameterReference)
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsXmlCommentsOnOperationsFromMinimalApis#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsXmlCommentsOnOperationsFromMinimalApis#OpenApiXmlCommentSupport.generated.verified.cs
index 85d5e91dd378..791bbee9c2aa 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsXmlCommentsOnOperationsFromMinimalApis#OpenApiXmlCommentSupport.generated.verified.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/OperationTests.SupportsXmlCommentsOnOperationsFromMinimalApis#OpenApiXmlCommentSupport.generated.verified.cs
@@ -1,4 +1,4 @@
-//HintName: OpenApiXmlCommentSupport.generated.cs
+//HintName: OpenApiXmlCommentSupport.generated.cs
 //------------------------------------------------------------------------------
 // <auto-generated>
 //     This code was generated by a tool.
@@ -39,6 +39,7 @@ namespace Microsoft.AspNetCore.OpenApi.Generated
     using System.Threading.Tasks;
     using Microsoft.AspNetCore.OpenApi;
     using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
     using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
     using Microsoft.Extensions.DependencyInjection;
     using Microsoft.OpenApi;
@@ -83,6 +84,7 @@ private static Dictionary<string, XmlComment> GenerateCacheEntries()
             cache.Add(@"P:MixedParametersClass.Age", new XmlComment(@"The user's age in years.", null, null, null, null, false, [@"25"], null, null));
             cache.Add(@"P:MixedParametersClass.IsActive", new XmlComment(@"Whether the user is active.", null, null, null, null, false, [@"true"], null, null));
             cache.Add(@"P:BindingSourceParametersClass.QueryParam", new XmlComment(@"Query parameter from URL.", null, null, null, null, false, null, null, null));
+            cache.Add(@"P:BindingSourceParametersClass.QueryParamWithCustomName", new XmlComment(@"Query parameter from URL with custom name.", null, null, null, null, false, null, null, null));
             cache.Add(@"P:BindingSourceParametersClass.HeaderParam", new XmlComment(@"Header value from request.", null, null, null, null, false, null, null, null));
             cache.Add(@"P:XmlDocPriorityParametersClass.SummaryOnlyProperty", new XmlComment(@"Property with only summary documentation.", null, null, null, null, false, null, null, null));
             cache.Add(@"P:XmlDocPriorityParametersClass.SummaryAndReturnsProperty", new XmlComment(@"Property with summary documentation that should be overridden.", null, null, @"Returns-based description that should take precedence over summary.", null, false, null, null, null));
@@ -183,30 +185,6 @@ public static string CreateDocumentationId(this PropertyInfo property)
             return sb.ToString();
         }
 
-        /// <summary>
-        /// Generates a documentation comment ID for a property given its container type and property name.
-        /// Example: P:Namespace.ContainingType.PropertyName
-        /// </summary>
-        public static string CreateDocumentationId(Type containerType, string propertyName)
-        {
-            if (containerType == null)
-            {
-                throw new ArgumentNullException(nameof(containerType));
-            }
-            if (string.IsNullOrEmpty(propertyName))
-            {
-                throw new ArgumentException("Property name cannot be null or empty.", nameof(propertyName));
-            }
-
-            var sb = new StringBuilder();
-            sb.Append("P:");
-            sb.Append(GetTypeDocId(containerType, includeGenericArguments: false, omitGenericArity: false));
-            sb.Append('.');
-            sb.Append(propertyName);
-
-            return sb.ToString();
-        }
-
         /// <summary>
         /// Generates a documentation comment ID for a method (or constructor).
         /// For example:
@@ -419,7 +397,7 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     foreach (var parameterComment in methodComment.Parameters)
                     {
                         var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
-                        var operationParameter = operation.Parameters?.SingleOrDefault(parameter => parameter.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
                         if (operationParameter is not null)
                         {
                             var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
@@ -430,7 +408,10 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                             }
                             targetOperationParameter.Deprecated = parameterComment.Deprecated;
                         }
-                        else
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
                         {
                             var requestBody = operation.RequestBody;
                             if (requestBody is not null)
@@ -479,10 +460,14 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     && metadata.ContainerType is { } containerType
                     && metadata.PropertyName is { } propertyName)
                 {
-                    var propertyDocId = DocumentationCommentIdHelper.CreateDocumentationId(containerType, propertyName);
-                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyDocId), out var propertyComment))
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
                     {
-                        var parameter = operation.Parameters?.SingleOrDefault(p => p.Name == metadata.Name);
+                        var parameter = GetOperationParameter(operation, propertyInfo);
                         var description = propertyComment.Summary;
                         if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
                         {
@@ -529,6 +514,86 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
             return Task.CompletedTask;
         }
 
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
         private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
         {
             if (sourceParameter is OpenApiParameterReference parameterReference)
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/SchemaTests.SupportsXmlCommentsOnSchemas#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/SchemaTests.SupportsXmlCommentsOnSchemas#OpenApiXmlCommentSupport.generated.verified.cs
index 9f6a292f13bb..8fe948f0e190 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/SchemaTests.SupportsXmlCommentsOnSchemas#OpenApiXmlCommentSupport.generated.verified.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/SchemaTests.SupportsXmlCommentsOnSchemas#OpenApiXmlCommentSupport.generated.verified.cs
@@ -1,4 +1,4 @@
-//HintName: OpenApiXmlCommentSupport.generated.cs
+//HintName: OpenApiXmlCommentSupport.generated.cs
 //------------------------------------------------------------------------------
 // <auto-generated>
 //     This code was generated by a tool.
@@ -39,6 +39,7 @@ namespace Microsoft.AspNetCore.OpenApi.Generated
     using System.Threading.Tasks;
     using Microsoft.AspNetCore.OpenApi;
     using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
     using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
     using Microsoft.Extensions.DependencyInjection;
     using Microsoft.OpenApi;
@@ -165,30 +166,6 @@ public static string CreateDocumentationId(this PropertyInfo property)
             return sb.ToString();
         }
 
-        /// <summary>
-        /// Generates a documentation comment ID for a property given its container type and property name.
-        /// Example: P:Namespace.ContainingType.PropertyName
-        /// </summary>
-        public static string CreateDocumentationId(Type containerType, string propertyName)
-        {
-            if (containerType == null)
-            {
-                throw new ArgumentNullException(nameof(containerType));
-            }
-            if (string.IsNullOrEmpty(propertyName))
-            {
-                throw new ArgumentException("Property name cannot be null or empty.", nameof(propertyName));
-            }
-
-            var sb = new StringBuilder();
-            sb.Append("P:");
-            sb.Append(GetTypeDocId(containerType, includeGenericArguments: false, omitGenericArity: false));
-            sb.Append('.');
-            sb.Append(propertyName);
-
-            return sb.ToString();
-        }
-
         /// <summary>
         /// Generates a documentation comment ID for a method (or constructor).
         /// For example:
@@ -401,7 +378,7 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     foreach (var parameterComment in methodComment.Parameters)
                     {
                         var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
-                        var operationParameter = operation.Parameters?.SingleOrDefault(parameter => parameter.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
                         if (operationParameter is not null)
                         {
                             var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
@@ -412,7 +389,10 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                             }
                             targetOperationParameter.Deprecated = parameterComment.Deprecated;
                         }
-                        else
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
                         {
                             var requestBody = operation.RequestBody;
                             if (requestBody is not null)
@@ -461,10 +441,14 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     && metadata.ContainerType is { } containerType
                     && metadata.PropertyName is { } propertyName)
                 {
-                    var propertyDocId = DocumentationCommentIdHelper.CreateDocumentationId(containerType, propertyName);
-                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyDocId), out var propertyComment))
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
                     {
-                        var parameter = operation.Parameters?.SingleOrDefault(p => p.Name == metadata.Name);
+                        var parameter = GetOperationParameter(operation, propertyInfo);
                         var description = propertyComment.Summary;
                         if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
                         {
@@ -511,6 +495,86 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
             return Task.CompletedTask;
         }
 
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
         private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
         {
             if (sourceParameter is OpenApiParameterReference parameterReference)
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/SchemaTests.XmlCommentsOnPropertiesShouldApplyToSchemaReferences#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/SchemaTests.XmlCommentsOnPropertiesShouldApplyToSchemaReferences#OpenApiXmlCommentSupport.generated.verified.cs
index be4687040128..530890b9ccf5 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/SchemaTests.XmlCommentsOnPropertiesShouldApplyToSchemaReferences#OpenApiXmlCommentSupport.generated.verified.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/SchemaTests.XmlCommentsOnPropertiesShouldApplyToSchemaReferences#OpenApiXmlCommentSupport.generated.verified.cs
@@ -1,4 +1,4 @@
-//HintName: OpenApiXmlCommentSupport.generated.cs
+//HintName: OpenApiXmlCommentSupport.generated.cs
 //------------------------------------------------------------------------------
 // <auto-generated>
 //     This code was generated by a tool.
@@ -39,6 +39,7 @@ namespace Microsoft.AspNetCore.OpenApi.Generated
     using System.Threading.Tasks;
     using Microsoft.AspNetCore.OpenApi;
     using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
     using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
     using Microsoft.Extensions.DependencyInjection;
     using Microsoft.OpenApi;
@@ -144,30 +145,6 @@ public static string CreateDocumentationId(this PropertyInfo property)
             return sb.ToString();
         }
 
-        /// <summary>
-        /// Generates a documentation comment ID for a property given its container type and property name.
-        /// Example: P:Namespace.ContainingType.PropertyName
-        /// </summary>
-        public static string CreateDocumentationId(Type containerType, string propertyName)
-        {
-            if (containerType == null)
-            {
-                throw new ArgumentNullException(nameof(containerType));
-            }
-            if (string.IsNullOrEmpty(propertyName))
-            {
-                throw new ArgumentException("Property name cannot be null or empty.", nameof(propertyName));
-            }
-
-            var sb = new StringBuilder();
-            sb.Append("P:");
-            sb.Append(GetTypeDocId(containerType, includeGenericArguments: false, omitGenericArity: false));
-            sb.Append('.');
-            sb.Append(propertyName);
-
-            return sb.ToString();
-        }
-
         /// <summary>
         /// Generates a documentation comment ID for a method (or constructor).
         /// For example:
@@ -380,7 +357,7 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     foreach (var parameterComment in methodComment.Parameters)
                     {
                         var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
-                        var operationParameter = operation.Parameters?.SingleOrDefault(parameter => parameter.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
                         if (operationParameter is not null)
                         {
                             var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
@@ -391,7 +368,10 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                             }
                             targetOperationParameter.Deprecated = parameterComment.Deprecated;
                         }
-                        else
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
                         {
                             var requestBody = operation.RequestBody;
                             if (requestBody is not null)
@@ -440,10 +420,14 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     && metadata.ContainerType is { } containerType
                     && metadata.PropertyName is { } propertyName)
                 {
-                    var propertyDocId = DocumentationCommentIdHelper.CreateDocumentationId(containerType, propertyName);
-                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyDocId), out var propertyComment))
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
                     {
-                        var parameter = operation.Parameters?.SingleOrDefault(p => p.Name == metadata.Name);
+                        var parameter = GetOperationParameter(operation, propertyInfo);
                         var description = propertyComment.Summary;
                         if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
                         {
@@ -490,6 +474,86 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
             return Task.CompletedTask;
         }
 
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
         private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
         {
             if (sourceParameter is OpenApiParameterReference parameterReference)
diff --git a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/XmlCommentDocumentationIdTests.CanMergeXmlCommentsWithDifferentDocumentationIdFormats#OpenApiXmlCommentSupport.generated.verified.cs b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/XmlCommentDocumentationIdTests.CanMergeXmlCommentsWithDifferentDocumentationIdFormats#OpenApiXmlCommentSupport.generated.verified.cs
index 14e6fc1de407..5d806270a95f 100644
--- a/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/XmlCommentDocumentationIdTests.CanMergeXmlCommentsWithDifferentDocumentationIdFormats#OpenApiXmlCommentSupport.generated.verified.cs
+++ b/src/OpenApi/test/Microsoft.AspNetCore.OpenApi.SourceGenerators.Tests/snapshots/XmlCommentDocumentationIdTests.CanMergeXmlCommentsWithDifferentDocumentationIdFormats#OpenApiXmlCommentSupport.generated.verified.cs
@@ -1,4 +1,4 @@
-//HintName: OpenApiXmlCommentSupport.generated.cs
+//HintName: OpenApiXmlCommentSupport.generated.cs
 //------------------------------------------------------------------------------
 // <auto-generated>
 //     This code was generated by a tool.
@@ -39,6 +39,7 @@ namespace Microsoft.AspNetCore.OpenApi.Generated
     using System.Threading.Tasks;
     using Microsoft.AspNetCore.OpenApi;
     using Microsoft.AspNetCore.Mvc.Controllers;
+    using Microsoft.AspNetCore.Mvc.ModelBinding;
     using Microsoft.AspNetCore.Mvc.ModelBinding.Metadata;
     using Microsoft.Extensions.DependencyInjection;
     using Microsoft.OpenApi;
@@ -136,30 +137,6 @@ public static string CreateDocumentationId(this PropertyInfo property)
             return sb.ToString();
         }
 
-        /// <summary>
-        /// Generates a documentation comment ID for a property given its container type and property name.
-        /// Example: P:Namespace.ContainingType.PropertyName
-        /// </summary>
-        public static string CreateDocumentationId(Type containerType, string propertyName)
-        {
-            if (containerType == null)
-            {
-                throw new ArgumentNullException(nameof(containerType));
-            }
-            if (string.IsNullOrEmpty(propertyName))
-            {
-                throw new ArgumentException("Property name cannot be null or empty.", nameof(propertyName));
-            }
-
-            var sb = new StringBuilder();
-            sb.Append("P:");
-            sb.Append(GetTypeDocId(containerType, includeGenericArguments: false, omitGenericArity: false));
-            sb.Append('.');
-            sb.Append(propertyName);
-
-            return sb.ToString();
-        }
-
         /// <summary>
         /// Generates a documentation comment ID for a method (or constructor).
         /// For example:
@@ -372,7 +349,7 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     foreach (var parameterComment in methodComment.Parameters)
                     {
                         var parameterInfo = methodInfo.GetParameters().SingleOrDefault(info => info.Name == parameterComment.Name);
-                        var operationParameter = operation.Parameters?.SingleOrDefault(parameter => parameter.Name == parameterComment.Name);
+                        var operationParameter = GetOperationParameter(operation, parameterInfo, parameterComment);
                         if (operationParameter is not null)
                         {
                             var targetOperationParameter = UnwrapOpenApiParameter(operationParameter);
@@ -383,7 +360,10 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                             }
                             targetOperationParameter.Deprecated = parameterComment.Deprecated;
                         }
-                        else
+                        // Only fall back to the request body when the parameter is actually bound to it.
+                        // This avoids applying documentation for parameters that aren't part of the
+                        // OpenAPI surface (e.g. a `CancellationToken`) to the request body.
+                        else if (IsRequestBodyParameter(context, parameterInfo, parameterComment))
                         {
                             var requestBody = operation.RequestBody;
                             if (requestBody is not null)
@@ -432,10 +412,14 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
                     && metadata.ContainerType is { } containerType
                     && metadata.PropertyName is { } propertyName)
                 {
-                    var propertyDocId = DocumentationCommentIdHelper.CreateDocumentationId(containerType, propertyName);
-                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyDocId), out var propertyComment))
+                    var propertyInfo = containerType.GetProperty(propertyName);
+                    if (propertyInfo is null)
+                    {
+                        continue;
+                    }
+                    if (XmlCommentCache.Cache.TryGetValue(DocumentationCommentIdHelper.NormalizeDocId(propertyInfo.CreateDocumentationId()), out var propertyComment))
                     {
-                        var parameter = operation.Parameters?.SingleOrDefault(p => p.Name == metadata.Name);
+                        var parameter = GetOperationParameter(operation, propertyInfo);
                         var description = propertyComment.Summary;
                         if (!string.IsNullOrEmpty(description) && !string.IsNullOrEmpty(propertyComment.Value))
                         {
@@ -482,6 +466,86 @@ public Task TransformAsync(OpenApiOperation operation, OpenApiOperationTransform
             return Task.CompletedTask;
         }
 
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, PropertyInfo propertyInfo)
+        {
+            return GetOperationParameter(operation, propertyInfo, propertyInfo?.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            return GetOperationParameter(operation, parameterInfo, parameterInfo?.Name ?? comment.Name);
+        }
+
+        private static IOpenApiParameter? GetOperationParameter(OpenApiOperation operation, ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var parameters = operation.Parameters;
+            if (parameters is null || parameters.Count == 0)
+            {
+                return null;
+            }
+
+            var modelNames = GetModelNames(attributeProvider, name);
+
+            foreach (var parameter in parameters)
+            {
+                var parameterName = parameter.Name;
+
+                if (string.IsNullOrEmpty(parameterName))
+                {
+                    continue;
+                }
+
+                if (modelNames.Contains(parameterName))
+                {
+                    return parameter;
+                }
+            }
+
+            return null;
+        }
+
+        private static bool IsRequestBodyParameter(OpenApiOperationTransformerContext context, ParameterInfo? parameterInfo, XmlParameterComment comment)
+        {
+            var modelNames = GetModelNames(parameterInfo, parameterInfo?.Name ?? comment.Name);
+
+            foreach (var parameterDescription in context.Description.ParameterDescriptions)
+            {
+                if (parameterDescription.Source == BindingSource.Body
+                    && parameterDescription.Name is { } parameterName
+                    && modelNames.Contains(parameterName))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
+        private static IReadOnlySet<string> GetModelNames(ICustomAttributeProvider? attributeProvider, string? name)
+        {
+            var modelNames = new HashSet<string>();
+
+            if (!string.IsNullOrEmpty(name))
+            {
+                modelNames.Add(name);
+            }
+
+            if (attributeProvider is null)
+            {
+                return modelNames;
+            }
+
+            foreach (var attribute in attributeProvider.GetCustomAttributes(inherit: false))
+            {
+                if (attribute is IModelNameProvider modelNameProvider && !string.IsNullOrEmpty(modelNameProvider.Name))
+                {
+                    modelNames.Add(modelNameProvider.Name);
+                }
+            }
+
+            return modelNames;
+        }
+
         private static OpenApiParameter UnwrapOpenApiParameter(IOpenApiParameter sourceParameter)
         {
             if (sourceParameter is OpenApiParameterReference parameterReference)