Question: Invoke notification within a tool call

[ahmedhesham6]

I’m using the SDK and need a way to invoke a notification from inside a tool call so I can stream progress updates back to the user. Right now the tool handler doesn’t have access to the request context, so I can’t call the function.

Is there an existing API or pattern for this? If context injection in tools isn’t supported yet, I’d be happy to help implement it.

[4t145]

It's on my todo list. Someone also mentioned it at here #195 (comment).

[ahmedhesham6]

How can I help ?

[4t145]

@ahmedhesham6 This isn't a lot of work, so helping review the code would be great.

[4t145]

#236 merged. Now you can get peer when handling tool call, and get peer when hanlding notification.
cc @Pluto-Y

[VakeDomen]

I'm not sure if I'm just missing something obvious but i have the same problem and can't figure this out for the life of me.

I'm using #[tool(tool_box)] to implement tools for a service but i can't seem to get to the NotificationContext inside a tool fn. I was thinking maybe I can just save the context into the struct itself when on_initialize triggers, but since self is not mutable I can't. I was thinking that it's probably possible to clone the context and save it to an external data structure, but this just seems like I'm doing everything completely wrong.

Is there an example I could look at to get this to work?

[4t145]

@VakeDomen you can only get RequestContext in a tool fn. You are not supposed to store a context, it's generated per request/ per notification.

[VakeDomen]

@4t145 yes, this makes sense.
What I don't understand is how to get access to RequestContext inside the fn.
For example:

#[derive(Debug, Clone)]
struct Service;


#[tool(tool_box)]
impl Service {
    #[tool(description = "Tool without context")]
    pub async fn do_work(&self, #[tool(aggr)] question: StructRequest) -> Result<CallToolResult, rmcp::Error> {
        // notify
        
        work();

        // notify

        work();

        // notify

        work();
        Ok(CallToolResult::success(vec![Content::text("hello")]))
    }
}

#[tool(tool_box)]
impl ServerHandler for Service {
    fn get_info(&self) -> ServerInfo {
        ServerInfo {
            instructions: Some("Sample service".into()),
            capabilities: ServerCapabilities::builder().enable_tools().build(),
            ..Default::default()
        }
    }
}

How do we notify the client of progress from the do_work tool?

[4t145]

@VakeDomen just add it as a parameter

#[tool(tool_box)]
impl Service {
    #[tool(description = "Tool without context")]
    pub async fn do_work(&self, #[tool(aggr)] question: StructRequest, ctx: RequestContext<RoleServer>) -> Result<CallToolResult, rmcp::Error> {
        // notify
        
        work();

        // notify

        work();

        // notify

        work();
        Ok(CallToolResult::success(vec![Content::text("hello")]))
    }
}