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Callable methods

Callable methods let clients invoke agent methods over WebSocket using RPC (Remote Procedure Call). Mark methods with @callable() to expose them to external clients like browsers, mobile apps, or other services.

Overview

JavaScript
import { Agent, callable } from "agents";


export class MyAgent extends Agent {
  @callable()
  async greet(name) {
    return `Hello, ${name}!`;
  }
}
JavaScript
// Client
const result = await agent.stub.greet("World");
console.log(result); // "Hello, World!"

How it works

sequenceDiagram
    participant Client
    participant Agent
    Client->>Agent: agent.stub.greet("World")
    Note right of Agent: Check @callable<br/>Execute method
    Agent-->>Client: "Hello, World!"

When to use @callable()

ScenarioUse
Browser/mobile calling agent@callable()
External service calling agent@callable()
Worker calling agent (same codebase)Durable Object RPC (no decorator needed)
Agent calling another agentDurable Object RPC via getAgentByName()

The @callable() decorator is specifically for WebSocket-based RPC from external clients. When calling from within the same Worker or another agent, use standard Durable Object RPC directly.

Basic usage

Defining callable methods

Add the @callable() decorator to any method you want to expose:

JavaScript
import { Agent, callable } from "agents";


export class CounterAgent extends Agent {
  initialState = { count: 0, items: [] };


  @callable()
  increment() {
    this.setState({ ...this.state, count: this.state.count + 1 });
    return this.state.count;
  }


  @callable()
  decrement() {
    this.setState({ ...this.state, count: this.state.count - 1 });
    return this.state.count;
  }


  @callable()
  async addItem(item) {
    this.setState({ ...this.state, items: [...this.state.items, item] });
    return this.state.items;
  }


  @callable()
  getStats() {
    return {
      count: this.state.count,
      itemCount: this.state.items.length,
    };
  }
}

Calling from the client

There are two ways to call methods from the client:

JavaScript
// Clean, typed syntax
const count = await agent.stub.increment();
const items = await agent.stub.addItem("new item");
const stats = await agent.stub.getStats();

Using agent.call():

JavaScript
// Explicit method name as string
const count = await agent.call("increment");
const items = await agent.call("addItem", ["new item"]);
const stats = await agent.call("getStats");

The stub proxy provides better ergonomics and TypeScript support.

Method signatures

Serializable types

Arguments and return values must be JSON-serializable:

JavaScript
// Valid - primitives and plain objects
class MyAgent extends Agent {
  @callable()
  processData(input) {
    return { result: true };
  }
}


// Valid - arrays
class MyAgent extends Agent {
  @callable()
  processItems(items) {
    return items.map((item) => item.length);
  }
}


// Invalid - non-serializable types
// Functions, Dates, Maps, Sets, etc. cannot be serialized

Async methods

Both sync and async methods work:

JavaScript
// Sync method
class MyAgent extends Agent {
  @callable()
  add(a, b) {
    return a + b;
  }
}


// Async method
class MyAgent extends Agent {
  @callable()
  async fetchUser(id) {
    const user = await this.sql`SELECT * FROM users WHERE id = ${id}`;
    return user[0];
  }
}

Void methods

Methods that do not return a value:

JavaScript
class MyAgent extends Agent {
  @callable()
  async logEvent(event) {
    await this.sql`INSERT INTO events (name) VALUES (${event})`;
  }
}

On the client, these still return a Promise that resolves when the method completes:

JavaScript
await agent.stub.logEvent("user-clicked");
// Resolves when the server confirms execution

Streaming responses

For methods that produce data over time (like AI text generation), use streaming:

Defining a streaming method

JavaScript
import { Agent, callable } from "agents";


export class AIAgent extends Agent {
  @callable({ streaming: true })
  async generateText(stream, prompt) {
    // First parameter is always StreamingResponse for streaming methods


    for await (const chunk of this.llm.stream(prompt)) {
      stream.send(chunk); // Send each chunk to the client
    }


    stream.end(); // Signal completion
  }


  @callable({ streaming: true })
  async streamNumbers(stream, count) {
    for (let i = 0; i < count; i++) {
      stream.send(i);
      await new Promise((resolve) => setTimeout(resolve, 100));
    }
    stream.end(count); // Optional final value
  }
}

Consuming streams on the client

JavaScript
// Preferred format (supports timeout and other options)
await agent.call("generateText", [prompt], {
  stream: {
    onChunk: (chunk) => {
      // Called for each chunk
      appendToOutput(chunk);
    },
    onDone: (finalValue) => {
      // Called when stream ends
      console.log("Stream complete", finalValue);
    },
    onError: (error) => {
      // Called if an error occurs
      console.error("Stream error:", error);
    },
  },
});


// Legacy format (still supported for backward compatibility)
await agent.call("generateText", [prompt], {
  onChunk: (chunk) => appendToOutput(chunk),
  onDone: (finalValue) => console.log("Done", finalValue),
  onError: (error) => console.error("Error:", error),
});

StreamingResponse API

MethodDescription
send(chunk)Send a chunk to the client
end(finalChunk?)End the stream, optionally with a final value
error(message)Send an error to the client and close the stream
JavaScript
class MyAgent extends Agent {
  @callable({ streaming: true })
  async processWithProgress(stream, items) {
    for (let i = 0; i < items.length; i++) {
      await this.process(items[i]);
      stream.send({ progress: (i + 1) / items.length, item: items[i] });
    }
    stream.end({ completed: true, total: items.length });
  }
}

TypeScript integration

Typed client calls

Pass your agent class as a type parameter for full type safety:

JavaScript
import { useAgent } from "agents/react";
function App() {
  const agent = useAgent({
    agent: "MyAgent",
    name: "default",
  });


  async function handleGreet(result) {
    // TypeScript knows the method signature
    const result = await agent.stub.greet("World");
    // ^? string
  }


  // TypeScript catches errors
  // await agent.stub.greet(123); // Error: Argument of type 'number' is not assignable
  // await agent.stub.nonExistent(); // Error: Property 'nonExistent' does not exist
}

Excluding non-callable methods

If you have methods that are not decorated with @callable(), you can exclude them from the type:

JavaScript
class MyAgent extends Agent {
  @callable()
  publicMethod() {
    return "public";
  }


  // Not callable from clients
  internalMethod() {
    // internal logic
  }
}


// Exclude internal methods from the client type
const agent = useAgent({
  agent: "MyAgent",
});


agent.stub.publicMethod(); // Works
// agent.stub.internalMethod(); // TypeScript error

Error handling

Throwing errors in callable methods

Errors thrown in callable methods are propagated to the client:

JavaScript
class MyAgent extends Agent {
  @callable()
  async riskyOperation(data) {
    if (!isValid(data)) {
      throw new Error("Invalid data format");
    }


    try {
      await this.processData(data);
    } catch (e) {
      throw new Error("Processing failed: " + e.message);
    }
  }
}

Client-side error handling

JavaScript
try {
  const result = await agent.stub.riskyOperation(data);
} catch (error) {
  // Error thrown by the agent method
  console.error("RPC failed:", error.message);
}

Streaming error handling

For streaming methods, use the onError callback:

JavaScript
await agent.call("streamData", [input], {
  stream: {
    onChunk: (chunk) => handleChunk(chunk),
    onError: (errorMessage) => {
      console.error("Stream error:", errorMessage);
      showErrorUI(errorMessage);
    },
    onDone: (result) => handleComplete(result),
  },
});

Server-side, you can use stream.error() to gracefully send an error mid-stream:

JavaScript
class MyAgent extends Agent {
  @callable({ streaming: true })
  async processItems(stream, items) {
    for (const item of items) {
      try {
        const result = await this.process(item);
        stream.send(result);
      } catch (e) {
        stream.error(`Failed to process ${item}: ${e.message}`);
        return; // Stream is now closed
      }
    }
    stream.end();
  }
}

Connection errors

If the WebSocket connection closes while RPC calls are pending, they automatically reject with a "Connection closed" error:

JavaScript
try {
  const result = await agent.call("longRunningMethod", []);
} catch (error) {
  if (error.message === "Connection closed") {
    // Handle disconnection
    console.log("Lost connection to agent");
  }
}

Retrying after reconnection

The client automatically reconnects after disconnection. To retry a failed call after reconnection, await agent.ready before retrying:

JavaScript
async function callWithRetry(agent, method, args = []) {
  try {
    return await agent.call(method, args);
  } catch (error) {
    if (error.message === "Connection closed") {
      await agent.ready; // Wait for reconnection
      return await agent.call(method, args); // Retry once
    }
    throw error;
  }
}


// Usage
const result = await callWithRetry(agent, "processData", [data]);

When NOT to use @callable

Worker-to-Agent calls

When calling an agent from the same Worker (for example, in your fetch handler), use Durable Object RPC directly:

JavaScript
import { getAgentByName } from "agents";


export default {
  async fetch(request, env) {
    // Get the agent stub
    const agent = await getAgentByName(env.MyAgent, "instance-name");


    // Call methods directly - no @callable needed
    const result = await agent.processData(data);


    return Response.json(result);
  },
};

Agent-to-Agent calls

When one agent needs to call another:

JavaScript
class OrchestratorAgent extends Agent {
  async delegateWork(taskId) {
    // Get another agent
    const worker = await getAgentByName(this.env.WorkerAgent, taskId);


    // Call its methods directly
    const result = await worker.doWork();


    return result;
  }
}

Why the distinction?

RPC TypeTransportUse Case
@callableWebSocketExternal clients (browsers, apps)
Durable Object RPCInternalWorker to Agent, Agent to Agent

Durable Object RPC is more efficient for internal calls since it does not go through WebSocket serialization. The @callable decorator adds the necessary WebSocket RPC handling for external clients.

API reference

@callable(metadata?) decorator

Marks a method as callable from external clients.

JavaScript
import { callable } from "agents";


class MyAgent extends Agent {
  @callable()
  method() {}


  @callable({ streaming: true })
  streamingMethod(stream) {}


  @callable({ description: "Fetches user data" })
  getUser(id) {}
}

CallableMetadata type

TypeScript
type CallableMetadata = {
  /** Optional description of what the method does */
  description?: string;
  /** Whether the method supports streaming responses */
  streaming?: boolean;
};

StreamingResponse class

Used in streaming callable methods to send data to the client.

JavaScript
import {} from "agents";


class MyAgent extends Agent {
  @callable({ streaming: true })
  async streamData(stream, input) {
    stream.send("chunk 1");
    stream.send("chunk 2");
    stream.end("final");
  }
}
MethodSignatureDescription
send(chunk: unknown) => voidSend a chunk to the client
end(finalChunk?: unknown) => voidEnd the stream
error(message: string) => voidSend an error and close the stream

Client methods

MethodSignatureDescription
agent.call(method, args?, options?) => PromiseCall a method by name
agent.stubProxyTyped method calls
JavaScript
// Using call()
await agent.call("methodName", [arg1, arg2]);
await agent.call("streamMethod", [arg], {
  stream: { onChunk, onDone, onError },
});


// With timeout (rejects if call does not complete in time)
await agent.call("slowMethod", [], { timeout: 5000 });


// Using stub
await agent.stub.methodName(arg1, arg2);

CallOptions type

TypeScript
type CallOptions = {
  /** Timeout in milliseconds. Rejects if call does not complete in time. */
  timeout?: number;
  /** Streaming options */
  stream?: {
    onChunk?: (chunk: unknown) => void;
    onDone?: (finalChunk: unknown) => void;
    onError?: (error: string) => void;
  };
};

getCallableMethods() method

Returns a map of all callable methods on the agent with their metadata. Useful for introspection and automatic documentation.

JavaScript
const methods = agent.getCallableMethods();
// Map<string, CallableMetadata>


for (const [name, meta] of methods) {
  console.log(`${name}: ${meta.description || "(no description)"}`);
  if (meta.streaming) console.log("  (streaming)");
}

Next steps

Agents API Complete API reference for the Agents SDK.
WebSockets Real-time bidirectional communication with clients.
State management Sync state between agents and clients.