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1. eratner15

   added a commit that references this issue on Apr 16, 2026

   v0.15.0: demo-ready — EDGAR fix, agent stabilized, bug filed

   ...

   6dc0727
2. eratner15 commented on Apr 16, 2026

   

   eratner15

   on Apr 16, 2026

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   Minimal reproduction: any Think agent using @ai-sdk/anthropic or @ai-sdk/openai with tool() + Zod v4 parameters. The zod-to-json-schema package (used internally by the AI SDK) returns {} for Zod v4 schemas, so the provider sends input_schema without type: 'object'. Both Anthropic and OpenAI APIs reject this.

   This blocks Think from working with any external LLM provider. Only Workers AI models work because they don't validate tool schemas strictly.

   Happy to help test a fix. cc @threepointone @geelen
3. threepointone commented on Apr 16, 2026

   

   threepointone

   on Apr 16, 2026

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   can you actually make a small repro? because this should just work, unless you're using older versions of any dependencies. happy to dive into it
4. eratner15 commented on Apr 16, 2026

   

   eratner15

   on Apr 16, 2026

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   Minimal repro

   Fresh project, all latest versions:

   @cloudflare/think: 0.2.4
   @ai-sdk/anthropic: 3.0.69
   agents: 0.11.1
   ai: 6.0.164
   zod: 4.3.6
   workers-ai-provider: 3.1.11
   

   wrangler.jsonc

   {
     "name": "think-anthropic-repro",
     "main": "src/index.ts",
     "compatibility_date": "2026-04-16",
     "compatibility_flags": ["nodejs_compat"],
     "durable_objects": {
       "bindings": [{ "class_name": "MyAgent", "name": "MyAgent" }]
     },
     "migrations": [{ "new_sqlite_classes": ["MyAgent"], "tag": "v1" }],
     "ai": { "binding": "AI" }
   }

   src/index.ts

   import { Think } from "@cloudflare/think";
   import { createAnthropic } from "@ai-sdk/anthropic";
   import { tool } from "ai";
   import { z } from "zod";
   import { routeAgentRequest } from "agents";
   
   interface Env { AI: any; ANTHROPIC_API_KEY: string; }
   
   export class MyAgent extends Think<Env> {
     maxSteps = 5;
   
     getModel() {
       return createAnthropic({ apiKey: this.env.ANTHROPIC_API_KEY })("claude-sonnet-4-20250514");
     }
   
     getSystemPrompt() { return "You are a helpful assistant with tools."; }
   
     async beforeTurn() { return { activeTools: ["get_weather"] }; }
   
     getTools() {
       return {
         get_weather: tool({
           description: "Get weather for a city",
           parameters: z.object({ city: z.string().describe("City name") }),
           execute: async ({ city }) => ({ city, temp: 72, condition: "sunny" }),
         }),
       };
     }
   }
   
   export default {
     async fetch(request: Request, env: Env) {
       return (await routeAgentRequest(request, env)) || new Response("Not found", { status: 404 });
     },
   } satisfies ExportedHandler<Env>;

   Steps

   1. Deploy with npx wrangler deploy
   2. Set ANTHROPIC_API_KEY secret
   3. Connect via WebSocket to /agents/my-agent/test1
   4. Send cf_agent_use_chat_request with any message

   Result

   tools.0.custom.input_schema.type: Field required
   

   Same error with @ai-sdk/openai + GPT-4o:

   Invalid schema for function 'get_weather': schema must be a JSON Schema of 'type: "object"', got 'type: "None"'.
   

   Root cause trace

   const { zodToJsonSchema } = require("zod-to-json-schema");
   const { z } = require("zod"); // v4.3.6
   console.log(zodToJsonSchema(z.object({ city: z.string() })));
   // → { "$schema": "http://json-schema.org/draft-07/schema#" }
   // Missing: type, properties, required — empty schema

   zod-to-json-schema doesn't support Zod v4. The AI SDK uses it internally to convert tool parameters before sending to providers. Zod v4 has a native .toJsonSchema() method that works correctly.

   Works fine with Workers AI models (kimi-k2.5) because they don't validate input_schema strictly. Breaks with any external provider (Anthropic, OpenAI) that validates schema shape.

   Live repro deployed at: think-anthropic-repro.evan-ratner.workers.dev
5. whoiskatrin

   added

   bugSomething isn't workingSomething isn't working

   on May 5, 2026
6. threepointone

   assigned

   cjol

   on Aug 5, 2026
7. threepointone commented on Aug 5, 2026

   

   threepointone

   on Aug 5, 2026

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   we should try to move to standard schema
8. cjol commented on Aug 5, 2026

   

   cjol

   on Aug 5, 2026

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   Hi @eratner15 . This actually isn't a zod problem. It looks like you're using parameters in the tool definition, which was correct syntax in AI SDK v4, but not in v6 as you've currently got installed. In v6, it's called inputSchema, and retrying your example with that line produces the correct JSON schema for both Anthropic and OpenAI.

   I'm going to close this, but please reopen if inputSchema doesn't work for you.
9. cjol

   closed this as completedon Aug 5, 2026