cloudflare-agents

What this skill does

# Cloudflare Agents SDK

**Status**: Production Ready ✅
**Last Updated**: 2025-10-21
**Dependencies**: cloudflare-worker-base (recommended)
**Latest Versions**: agents@latest, @modelcontextprotocol/sdk@latest
**Production Tested**: Cloudflare's own MCP servers (https://github.com/cloudflare/mcp-server-cloudflare)

---

## What is Cloudflare Agents?

The Cloudflare Agents SDK enables building AI-powered autonomous agents that run on Cloudflare Workers + Durable Objects. Agents can:

- **Communicate in real-time** via WebSockets and Server-Sent Events
- **Persist state** with built-in SQLite database (up to 1GB per agent)
- **Schedule tasks** using delays, specific dates, or cron expressions
- **Run workflows** by triggering asynchronous Cloudflare Workflows
- **Browse the web** using Browser Rendering API + Puppeteer
- **Implement RAG** with Vectorize vector database + Workers AI embeddings
- **Build MCP servers** implementing the Model Context Protocol
- **Support human-in-the-loop** patterns for review and approval
- **Scale to millions** of independent agent instances globally

Each agent instance is a **globally unique, stateful micro-server** that can run for seconds, minutes, or hours.

---

## Quick Start (10 Minutes)

### 1. Scaffold Project with Template

```bash
npm create cloudflare@latest my-agent -- \
  --template=cloudflare/agents-starter \
  --ts \
  --git \
  --deploy false
```

**What this creates:**
- Complete Agent project structure
- TypeScript configuration
- wrangler.jsonc with Durable Objects bindings
- Example chat agent implementation
- React client with useAgent hook

### 2. Or Add to Existing Worker

```bash
cd my-existing-worker
npm install agents
```

**Then create an Agent class:**

```typescript
// src/index.ts
import { Agent, AgentNamespace } from "agents";

export class MyAgent extends Agent {
  async onRequest(request: Request): Promise<Response> {
    return new Response("Hello from Agent!");
  }
}

export default MyAgent;
```

### 3. Configure Durable Objects Binding

Create or update `wrangler.jsonc`:

```jsonc
{
  "$schema": "node_modules/wrangler/config-schema.json",
  "name": "my-agent",
  "main": "src/index.ts",
  "compatibility_date": "2025-10-21",
  "compatibility_flags": ["nodejs_compat"],
  "durable_objects": {
    "bindings": [
      {
        "name": "MyAgent",        // MUST match class name
        "class_name": "MyAgent"   // MUST match exported class
      }
    ]
  },
  "migrations": [
    {
      "tag": "v1",
      "new_sqlite_classes": ["MyAgent"]  // CRITICAL: Enables SQLite storage
    }
  ]
}
```

**CRITICAL Configuration Rules:**
- ✅ `name` and `class_name` **MUST be identical**
- ✅ `new_sqlite_classes` **MUST be in first migration** (cannot add later)
- ✅ Agent class **MUST be exported** (or binding will fail)
- ✅ Migration tags **CANNOT be reused** (each migration needs unique tag)

### 4. Deploy

```bash
npx wrangler@latest deploy
```

Your agent is now running at: `https://my-agent.<subdomain>.workers.dev`

---

## Configuration Deep Dive

### Complete wrangler.jsonc Example

```jsonc
{
  "$schema": "node_modules/wrangler/config-schema.json",
  "name": "my-agent",
  "main": "src/index.ts",
  "account_id": "YOUR_ACCOUNT_ID",
  "compatibility_date": "2025-10-21",
  "compatibility_flags": ["nodejs_compat"],

  // Durable Objects configuration (REQUIRED)
  "durable_objects": {
    "bindings": [
      {
        "name": "MyAgent",
        "class_name": "MyAgent"
      }
    ]
  },

  // Migrations (REQUIRED)
  "migrations": [
    {
      "tag": "v1",
      "new_sqlite_classes": ["MyAgent"]  // Enables state persistence
    }
  ],

  // Optional: Workers AI binding (for AI model calls)
  "ai": {
    "binding": "AI"
  },

  // Optional: Vectorize binding (for RAG)
  "vectorize": {
    "bindings": [
      {
        "binding": "VECTORIZE",
        "index_name": "my-agent-vectors"
      }
    ]
  },

  // Optional: Browser Rendering binding (for web browsing)
  "browser": {
    "binding": "BROWSER"
  },

  // Optional: Workflows binding (for async workflows)
  "workflows": [
    {
      "name": "MY_WORKFLOW",
      "class_name": "MyWorkflow",
      "script_name": "my-workflow-script"  // If in different project
    }
  ],

  // Optional: D1 binding (for additional persistent data)
  "d1_databases": [
    {
      "binding": "DB",
      "database_name": "my-agent-db",
      "database_id": "your-database-id"
    }
  ],

  // Optional: R2 binding (for file storage)
  "r2_buckets": [
    {
      "binding": "BUCKET",
      "bucket_name": "my-agent-files"
    }
  ],

  // Optional: Environment variables
  "vars": {
    "ENVIRONMENT": "production"
  },

  // Optional: Secrets (set with: wrangler secret put KEY)
  // OPENAI_API_KEY, ANTHROPIC_API_KEY, etc.

  // Observability
  "observability": {
    "enabled": true
  }
}
```

### Migrations Best Practices

**Atomic Deployments**: Migrations are **atomic operations** - they cannot be gradually deployed.

```jsonc
{
  "migrations": [
    {
      "tag": "v1",
      "new_sqlite_classes": ["MyAgent"]  // Initial: enable SQLite
    },
    {
      "tag": "v2",
      "renamed_classes": [
        {"from": "MyAgent", "to": "MyRenamedAgent"}
      ]
    },
    {
      "tag": "v3",
      "deleted_classes": ["OldAgent"]
    },
    {
      "tag": "v4",
      "transferred_classes": [
        {
          "from": "AgentInOldScript",
          "from_script": "old-worker",
          "to": "AgentInNewScript"
        }
      ]
    }
  ]
}
```

**Migration Rules:**
- ✅ Each migration needs a unique `tag`
- ✅ Cannot enable SQLite on existing deployed class (must be in first migration)
- ✅ Migrations apply in order during deployment
- ✅ Cannot edit or remove previous migration tags
- ❌ Never deploy new migrations gradually (atomic only)

### Environment-Specific Migrations

```jsonc
{
  "migrations": [{"tag": "v1", "new_sqlite_classes": ["MyAgent"]}],
  "env": {
    "staging": {
      "migrations": [
        {"tag": "v1", "new_sqlite_classes": ["MyAgent"]},
        {"tag": "v2-staging", "renamed_classes": [{"from": "MyAgent", "to": "StagingAgent"}]}
      ]
    }
  }
}
```

---

## Agent Class API

The `Agent` class is the foundation of the Agents SDK. Extend it to create your agent.

### Basic Agent Structure

```typescript
import { Agent } from "agents";

interface Env {
  // Environment variables and bindings
  OPENAI_API_KEY: string;
  AI: Ai;
  VECTORIZE: Vectorize;
  DB: D1Database;
}

interface State {
  // Your agent's persistent state
  counter: number;
  messages: string[];
  lastUpdated: Date | null;
}

export class MyAgent extends Agent<Env, State> {
  // Optional: Set initial state (first time agent is created)
  initialState: State = {
    counter: 0,
    messages: [],
    lastUpdated: null
  };

  // Optional: Called when agent instance starts or wakes from hibernation
  async onStart() {
    console.log('Agent started:', this.name, 'State:', this.state);
  }

  // Handle HTTP requests
  async onRequest(request: Request): Promise<Response> {
    return Response.json({ message: "Hello from Agent", state: this.state });
  }

  // Handle WebSocket connections (optional)
  async onConnect(connection: Connection, ctx: ConnectionContext) {
    console.log('Client connected:', connection.id);
    // Connections are automatically accepted
  }

  // Handle WebSocket messages (optional)
  async onMessage(connection: Connection, message: WSMessage) {
    if (typeof message === 'string') {
      connection.send(`Echo: ${message}`);
    }
  }

  // Handle WebSocket errors (optional)
  async onError(connection: Connection, error: unknown): Promise<void> {
    console.error('Connection error:', error);
  }

  // Handle WebSocket close (optional)
  async onClose(connection: Connection, code: number, reason: string, wasClean: boolean): Promise<void> {
    console.log('Connection closed:', code, reason);
  }

  // Called when state is updated from any source (optional)
  onStateUpda