Agents SDK

1---
2name: agents-sdk
3description: 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.
4---
5 
6# Cloudflare Agents SDK
7 
8**STOP.** Your knowledge of the Agents SDK may be outdated. Prefer retrieval over pre-training for any Agents SDK task.
9 
10## Documentation
11 
12Fetch current docs from `https://github.com/cloudflare/agents/tree/main/docs` before implementing.
13 
14| Topic | Doc | Use for |
15|-------|-----|---------|
16| Getting started | `docs/getting-started.md` | First agent, project setup |
17| State | `docs/state.md` | `setState`, `validateStateChange`, persistence |
18| Routing | `docs/routing.md` | URL patterns, `routeAgentRequest`, `basePath` |
19| Callable methods | `docs/callable-methods.md` | `@callable`, RPC, streaming, timeouts |
20| Scheduling | `docs/scheduling.md` | `schedule()`, `scheduleEvery()`, cron |
21| Workflows | `docs/workflows.md` | `AgentWorkflow`, durable multi-step tasks |
22| HTTP/WebSockets | `docs/http-websockets.md` | Lifecycle hooks, hibernation |
23| Email | `docs/email.md` | Email routing, secure reply resolver |
24| MCP client | `docs/mcp-client.md` | Connecting to MCP servers |
25| MCP server | `docs/mcp-servers.md` | Building MCP servers with `McpAgent` |
26| Client SDK | `docs/client-sdk.md` | `useAgent`, `useAgentChat`, React hooks |
27| Human-in-the-loop | `docs/human-in-the-loop.md` | Approval flows, pausing workflows |
28| Resumable streaming | `docs/resumable-streaming.md` | Stream recovery on disconnect |
29 
30Cloudflare docs: https://developers.cloudflare.com/agents/
31 
32## Capabilities
33 
34The Agents SDK provides:
35 
36- **Persistent state** - SQLite-backed, auto-synced to clients
37- **Callable RPC** - `@callable()` methods invoked over WebSocket
38- **Scheduling** - One-time, recurring (`scheduleEvery`), and cron tasks
39- **Workflows** - Durable multi-step background processing via `AgentWorkflow`
40- **MCP integration** - Connect to MCP servers or build your own with `McpAgent`
41- **Email handling** - Receive and reply to emails with secure routing
42- **Streaming chat** - `AIChatAgent` with resumable streams
43- **React hooks** - `useAgent`, `useAgentChat` for client apps
44 
45## FIRST: Verify Installation
46 
47```bash
48npm ls agents  # Should show agents package
49```
50 
51If not installed:
52```bash
53npm install agents
54```
55 
56## Wrangler Configuration
57 
58```jsonc
59{
60  "durable_objects": {
61    "bindings": [{ "name": "MyAgent", "class_name": "MyAgent" }]
62  },
63  "migrations": [{ "tag": "v1", "new_sqlite_classes": ["MyAgent"] }]
64}
65```
66 
67## Agent Class
68 
69```typescript
70import { Agent, routeAgentRequest, callable } from "agents";
71 
72type State = { count: number };
73 
74export class Counter extends Agent<Env, State> {
75  initialState = { count: 0 };
76 
77  // Validation hook - runs before state persists (sync, throwing rejects the update)
78  validateStateChange(nextState: State, source: Connection | "server") {
79    if (nextState.count < 0) throw new Error("Count cannot be negative");
80  }
81 
82  // Notification hook - runs after state persists (async, non-blocking)
83  onStateUpdate(state: State, source: Connection | "server") {
84    console.log("State updated:", state);
85  }
86 
87  @callable()
88  increment() {
89    this.setState({ count: this.state.count + 1 });
90    return this.state.count;
91  }
92}
93 
94export default {
95  fetch: (req, env) => routeAgentRequest(req, env) ?? new Response("Not found", { status: 404 })
96};
97```
98 
99## Routing
100 
101Requests route to `/agents/{agent-name}/{instance-name}`:
102 
103| Class | URL |
104|-------|-----|
105| `Counter` | `/agents/counter/user-123` |
106| `ChatRoom` | `/agents/chat-room/lobby` |
107 
108Client: `useAgent({ agent: "Counter", name: "user-123" })`
109 
110## Core APIs
111 
112| Task | API |
113|------|-----|
114| Read state | `this.state.count` |
115| Write state | `this.setState({ count: 1 })` |
116| SQL query | `` this.sql`SELECT * FROM users WHERE id = ${id}` `` |
117| Schedule (delay) | `await this.schedule(60, "task", payload)` |
118| Schedule (cron) | `await this.schedule("0 * * * *", "task", payload)` |
119| Schedule (interval) | `await this.scheduleEvery(30, "poll")` |
120| RPC method | `@callable() myMethod() { ... }` |
121| Streaming RPC | `@callable({ streaming: true }) stream(res) { ... }` |
122| Start workflow | `await this.runWorkflow("ProcessingWorkflow", params)` |
123 
124## React Client
125 
126```tsx
127import { useAgent } from "agents/react";
128 
129function App() {
130  const [state, setLocalState] = useState({ count: 0 });
131 
132  const agent = useAgent({
133    agent: "Counter",
134    name: "my-instance",
135    onStateUpdate: (newState) => setLocalState(newState),
136    onIdentity: (name, agentType) => console.log(`Connected to ${name}`)
137  });
138 
139  return (
140    <button onClick={() => agent.setState({ count: state.count + 1 })}>
141      Count: {state.count}
142    </button>
143  );
144}
145```
146 
147## References
148 
149- **[references/workflows.md](references/workflows.md)** - Durable Workflows integration
150- **[references/callable.md](references/callable.md)** - RPC methods, streaming, timeouts
151- **[references/state-scheduling.md](references/state-scheduling.md)** - State persistence, scheduling
152- **[references/streaming-chat.md](references/streaming-chat.md)** - AIChatAgent, resumable streams
153- **[references/mcp.md](references/mcp.md)** - MCP server integration
154- **[references/email.md](references/email.md)** - Email routing and handling
155- **[references/codemode.md](references/codemode.md)** - Code Mode (experimental)
156