agents-sdk

name	agents-sdk
description	Build AI agents on Cloudflare Workers using the Agents SDK. Load when creating stateful agents, durable workflows, real-time WebSocket apps, scheduled tasks, MCP servers, or chat applications. Covers Agent class, state management, callable RPC, Workflows integration, and React hooks.

Cloudflare Agents SDK

STOP. Your knowledge of the Agents SDK may be outdated. Prefer retrieval over pre-training for any Agents SDK task.

Documentation

Fetch current docs from https://github.com/cloudflare/agents/tree/main/docs before implementing.

Topic	Doc	Use for
Getting started	docs/getting-started.md	First agent, project setup
State	docs/state.md	setState, validateStateChange, persistence
Routing	docs/routing.md	URL patterns, routeAgentRequest, basePath
Callable methods	docs/callable-methods.md	@callable, RPC, streaming, timeouts
Scheduling	docs/scheduling.md	schedule(), scheduleEvery(), cron
Workflows	docs/workflows.md	AgentWorkflow, durable multi-step tasks
HTTP/WebSockets	docs/http-websockets.md	Lifecycle hooks, hibernation
Email	docs/email.md	Email routing, secure reply resolver
MCP client	docs/mcp-client.md	Connecting to MCP servers
MCP server	docs/mcp-servers.md	Building MCP servers with McpAgent
Client SDK	docs/client-sdk.md	useAgent, useAgentChat, React hooks
Human-in-the-loop	docs/human-in-the-loop.md	Approval flows, pausing workflows
Resumable streaming	docs/resumable-streaming.md	Stream recovery on disconnect

Cloudflare docs: https://developers.cloudflare.com/agents/

Capabilities

The Agents SDK provides:

• Persistent state - SQLite-backed, auto-synced to clients
• Callable RPC - @callable() methods invoked over WebSocket
• Scheduling - One-time, recurring (scheduleEvery), and cron tasks
• Workflows - Durable multi-step background processing via AgentWorkflow
• MCP integration - Connect to MCP servers or build your own with McpAgent
• Email handling - Receive and reply to emails with secure routing
• Streaming chat - AIChatAgent with resumable streams
• React hooks - useAgent, useAgentChat for client apps

FIRST: Verify Installation

npm ls agents  # Should show agents package

If not installed:

npm install agents

Wrangler Configuration

{
  "durable_objects": {
    "bindings": [{ "name": "MyAgent", "class_name": "MyAgent" }],
  },
  "migrations": [{ "tag": "v1", "new_sqlite_classes": ["MyAgent"] }],
}

Agent Class

import { Agent, routeAgentRequest, callable } from "agents"

type State = { count: number }

export class Counter extends Agent<Env, State> {
  initialState = { count: 0 }

  // Validation hook - runs before state persists (sync, throwing rejects the update)
  validateStateChange(nextState: State, source: Connection | "server") {
    if (nextState.count < 0) throw new Error("Count cannot be negative")
  }

  // Notification hook - runs after state persists (async, non-blocking)
  onStateUpdate(state: State, source: Connection | "server") {
    console.log("State updated:", state)
  }

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

export default {
  fetch: (req, env) => routeAgentRequest(req, env) ?? new Response("Not found", { status: 404 }),
}

Routing

Requests route to /agents/{agent-name}/{instance-name}:

Class	URL
Counter	/agents/counter/user-123
ChatRoom	/agents/chat-room/lobby

Client: useAgent({ agent: "Counter", name: "user-123" })

Core APIs

Task	API
Read state	this.state.count
Write state	this.setState({ count: 1 })
SQL query	this.sql`SELECT * FROM users WHERE id = ${id}`
Schedule (delay)	await this.schedule(60, "task", payload)
Schedule (cron)	await this.schedule("0 * * * *", "task", payload)
Schedule (interval)	await this.scheduleEvery(30, "poll")
RPC method	@callable() myMethod() { ... }
Streaming RPC	@callable({ streaming: true }) stream(res) { ... }
Start workflow	await this.runWorkflow("ProcessingWorkflow", params)

React Client

import { useAgent } from "agents/react"

function App() {
  const [state, setLocalState] = useState({ count: 0 })

  const agent = useAgent({
    agent: "Counter",
    name: "my-instance",
    onStateUpdate: (newState) => setLocalState(newState),
    onIdentity: (name, agentType) => console.log(`Connected to ${name}`),
  })

  return <button onClick={() => agent.setState({ count: state.count + 1 })}>Count: {state.count}</button>
}

References

• references/workflows.md - Durable Workflows integration
• references/callable.md - RPC methods, streaming, timeouts
• references/state-scheduling.md - State persistence, scheduling
• references/streaming-chat.md - AIChatAgent, resumable streams
• references/mcp.md - MCP server integration
• references/email.md - Email routing and handling
• references/codemode.md - Code Mode (experimental)