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Agents SDK

CloudflareOfficialPublished by Cloudflare

  • Skill
  • Tool integration
  • Cloud and DevOps
  • Apache-2.0
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From the author

Build, debug, or review Cloudflare Agents SDK applications using the agents package.
— the description by Cloudflare

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides essential documentation and best practices for developing with the Cloudflare Agents SDK. It covers the full lifecycle of agent development, including state management, RPC communication via callable methods, durable execution, and background task scheduling. The resource is designed to help developers integrate agents into existing Workers applications, configure environments, and leverage advanced features like MCP integration, streaming chat, and experimental browser tools.

What it does

  • Provides setup instructions for the agents package and project configuration.
  • Explains how to implement persistent state and handle state updates.
  • Details the use of @callable decorators for WebSocket-based RPC.
  • Covers durable execution patterns like runFiber and background workflows.
  • Guides the integration of chat agents, streaming responses, and MCP servers.
  • Outlines observability, testing, and deployment configurations for agents.

When to use it

  • When building stateful, event-driven agents on the Cloudflare Workers platform.
  • When you need to expose agent methods to client applications via WebSocket RPC.
  • When implementing durable, multi-step background tasks or scheduled cron jobs.
  • When integrating external tools or MCP servers into your agentic workflows.
  • When debugging agent lifecycle events or state synchronization issues.

Advantages

  • Centralized access to official documentation and implementation patterns.
  • Clear guidance on avoiding common pitfalls like incorrect decorator usage.
  • Comprehensive coverage of both core APIs and experimental features.
  • Structured reference for complex topics like durable execution and retries.

Usage examples

“How do I define a callable method in my Cloudflare Agent?”
The agent will show how to use the @callable decorator on a class method to expose it for WebSocket RPC, including examples for both standard and streaming responses.
“What is the correct way to configure an agent in wrangler.jsonc?”
The agent will provide a JSON configuration snippet showing the required compatibility flags, durable object bindings, and migration settings.
“How can I persist state in my agent?”
The agent will explain the use of the state object, the setState method, and how to implement validateStateChange for data integrity.
“How do I run a background workflow in my agent?”
The agent will demonstrate using the runWorkflow method to trigger durable, multi-step background processing tasks.

Install

  1. Download the skill as a ZIP:

    https://mp-staging.autogineer.com/agent-skills/cloudflare/agents-sdk/download
  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip agents-sdk.zip -d .agents/skills

Documentation by Cloudflare

Cloudflare Agents SDK

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

Retrieval Sources

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

TopicDocs URLUse for
Getting startedQuick startFirst agent, project setup
Adding to existing projectAdd to existing projectInstall into existing Workers app
ConfigurationConfigurationwrangler.jsonc, bindings, assets, deployment
Agent classAgents APIAgent lifecycle, patterns, pitfalls
StateStore and sync statesetState, validateStateChange, persistence
RoutingRoutingURL patterns, routeAgentRequest
Callable methodsCallable methods@callable, RPC, streaming, timeouts
SchedulingSchedule tasksschedule(), scheduleEvery(), cron
WorkflowsRun workflowsAgentWorkflow, durable multi-step tasks
HTTP/WebSocketsWebSocketsLifecycle hooks, hibernation
Chat agentsChat agentsAIChatAgent, streaming, tools, persistence
Client SDKClient SDKuseAgent, AgentClient, state, RPC, HTTP
Client toolsClient toolsClient-side tools, autoContinueAfterToolResult
Server-driven messagesAutonomous responsessaveMessages, waitUntilStable, server-initiated turns
Resumable streamingChat agentsStream recovery on disconnect
EmailEmailEmail routing, secure reply resolver
MCP clientMCP clientConnecting to MCP servers
MCP serverMCP serverBuilding MCP servers with createMcpHandler
MCP transportsMCP transportsStreamable HTTP, SSE, RPC transport options
Securing MCP serversSecuring MCPOAuth, proxy MCP, hardening
Human-in-the-loopHuman-in-the-loopWorkflow approvals, elicitation, timeout handling
Durable executionDurable executionrunFiber(), stash(), surviving DO eviction
QueueQueueBuilt-in FIFO queue, queue()
RetriesRetriesthis.retry(), backoff/jitter
ObservabilityObservabilityDiagnostics-channel events
Push notificationsPush notificationsWeb Push + VAPID from agents
WebhooksWebhooksReceiving external webhooks
Cross-domain authCross-domain authWebSocket auth, tokens, CORS
Readonly connectionsReadonlyshouldConnectionBeReadonly
VoiceVoiceExperimental STT/TTS, withVoice
Browse the webBrowser toolsExperimental CDP browser automation
ThinkThinkExperimental higher-level chat agent class
MigrationsAI SDK v5, AI SDK v6Upgrading @cloudflare/ai-chat

Capabilities

The Agents SDK provides:

  • Persistent state — SQLite-backed, auto-synced to clients via setState

  • Callable RPC — @callable() methods invoked over WebSocket

  • Scheduling — One-time, recurring (scheduleEvery), and cron tasks

  • Workflows — Durable multi-step background processing via AgentWorkflow

  • Durable execution — runFiber() / stash() for work that survives DO eviction

  • Queue — Built-in FIFO queue with retries via queue()

  • Retries — this.retry() with exponential backoff and jitter

  • MCP integration — Connect to MCP servers or build your own with createMcpHandler

  • Email handling — Receive and reply to emails with secure routing

  • Streaming chat — AIChatAgent with resumable streams, message persistence, tools

  • Server-driven messages — saveMessages, waitUntilStable for proactive agent turns

  • React hooks — useAgent, useAgentChat for client apps

  • Observability — diagnostics_channel events for state, RPC, schedule, lifecycle

  • Push notifications — Web Push + VAPID delivery from agents

  • Webhooks — Receive and verify external webhooks

  • Voice (experimental) — STT/TTS via @cloudflare/voice

  • Browser tools (experimental) — CDP-powered browsing via agents/browser

  • Think (experimental) — Higher-level chat agent via @cloudflare/think

FIRST: Verify Installation

npm ls agents  # Should show agents package

If not installed:

npm install agents

For chat agents:

npm install agents @cloudflare/ai-chat ai @ai-sdk/react

Wrangler Configuration

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

Gotchas:

  • Do NOT enable experimentalDecorators in tsconfig (breaks @callable)

  • Never edit old migrations — always add new tags

  • Each agent class needs its own DO binding + migration entry

  • Add "ai": { "binding": "AI" } for Workers AI

Agent Class

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

type State = { count: number };

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

  validateStateChange(nextState: State, source: Connection | "server") {
    if (nextState.count < 0) throw new Error("Count cannot be negative");
  }

  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}:

ClassURL
Counter/agents/counter/user-123
ChatRoom/agents/chat-room/lobby

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

Custom routing: use getAgentByName(env.MyAgent, "instance-id") then agent.fetch(request).

Core APIs

TaskAPI
Read statethis.state.count
Write statethis.setState({ count: 1 })
SQL querythis.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 workflowawait this.runWorkflow("ProcessingWorkflow", params)
Durable fiberawait this.runFiber("name", async (ctx) => { ... })
Enqueue workthis.queue("handler", payload)
Retry with backoffawait this.retry(fn, { maxAttempts: 5 })
Broadcast to clientsthis.broadcast(message)
Get connectionsthis.getConnections(tag?)

React Client

Read client-sdk.md for client selection and current connection examples. For chat UI and tools, also read streaming-chat.md.

References

Core
Chat & Streaming
Background Processing
Integrations
Experimental

Skill feedback

If the user reports that this skill gave incorrect or outdated guidance, or is missing information, read references/skill-feedback.md.

Files

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Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs an MCP server, Needs Node.js

Security

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Attribution and licence

Published by
Cloudflare
Publisher
Cloudflare (Official)
Source
cloudflare/skills · skills/agents-sdk · commit 6eb6c78
Licence
Apache License 2.0 (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • ATTRIBUTION.md (written by AutoGineer)
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