TypeScript MCP Server on Cloudflare Workers

TypeScript MCP Server on Cloudflare Workers

Build production-ready Model Context Protocol (MCP) servers using TypeScript and deploy them on Cloudflare Workers. This skill covers the official @modelcontextprotocol/sdk, HTTP transport setup, authentication patterns, Cloudflare service integrations, and comprehensive error prevention.

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When to Use This Skill

Use this skill when:

• Building MCP servers to expose APIs, tools, or data to LLMs
• Deploying serverless MCP endpoints on Cloudflare Workers
• Integrating external APIs as MCP tools (REST, GraphQL, databases)
• Creating stateless MCP servers for edge deployment
• Exposing Cloudflare services (D1, KV, R2, Vectorize) via MCP protocol
• Implementing authenticated MCP servers with API keys, OAuth, or Zero Trust
• Building multi-tool MCP servers with resources and prompts
• Needing production-ready templates that prevent common MCP errors

Do NOT use this skill when:

• Building Python MCP servers (use FastMCP skill instead)
• Needing stateful agents with WebSockets (use Cloudflare Agents SDK)
• Wanting long-running persistent agents with SQLite storage (use Durable Objects)
• Building local CLI tools (use stdio transport, not HTTP)

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Core Concepts

MCP Protocol Components:

1. Tools - Functions LLMs can invoke (Zod schemas, async handlers, external APIs)
2. Resources - Data exposure (URI-based: config://app, user://{userId})
3. Prompts - Pre-configured templates for LLM interactions
4. Completions - Argument auto-complete (optional)

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Quick Start

1. Install Dependencies

bun add @modelcontextprotocol/sdk hono zod
bun add -d @cloudflare/workers-types wrangler typescript

2. Create Basic MCP Server

import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js';
import { Hono } from 'hono';
import { z } from 'zod';

const server = new McpServer({ name: 'my-mcp-server', version: '1.0.0' });

// Register a tool
server.registerTool(
  'echo',
  {
    description: 'Echoes back the input text',
    inputSchema: z.object({ text: z.string().describe('Text to echo') })
  },
  async ({ text }) => ({ content: [{ type: 'text', text }] })
);

// HTTP endpoint
const app = new Hono();

app.post('/mcp', async (c) => {
  const transport = new StreamableHTTPServerTransport({
    sessionIdGenerator: undefined,
    enableJsonResponse: true
  });

  // CRITICAL: Close transport to prevent memory leaks
  c.res.raw.on('close', () => transport.close());

  await server.connect(transport);
  await transport.handleRequest(c.req.raw, c.res.raw, await c.req.json());
  return c.body(null);
});

export default app;

3. Deploy

wrangler deploy

4. Use Production Templates

For complete implementations, copy from templates/ directory:

• templates/basic-mcp-server.ts - Minimal working server
• templates/tool-server.ts - Multiple tools (API integrations, calculations)
• templates/resource-server.ts - Static and dynamic resources
• templates/full-server.ts - Complete server (tools + resources + prompts)
• templates/authenticated-server.ts - Production security with API key authentication
• templates/wrangler.jsonc - Cloudflare Workers configuration

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Authentication Patterns

Quick Example - API Key Authentication (Most Common):

app.use('/mcp', async (c, next) => {
  const authHeader = c.req.header('Authorization');
  if (!authHeader?.startsWith('Bearer ')) {
    return c.json({ error: 'Unauthorized' }, 401);
  }

  const apiKey = authHeader.replace('Bearer ', '');
  const isValid = await c.env.MCP_API_KEYS.get(`key:${apiKey}`);
  if (!isValid) return c.json({ error: 'Invalid API key' }, 403);

  await next();
});

For complete authentication guide: Load references/authentication-guide.md when implementing production authentication. Covers 5 methods: API Key (recommended), Cloudflare Zero Trust Access, OAuth 2.0, JWT custom, and mTLS. Includes security best practices, testing strategies, and migration guides.

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Cloudflare Service Integration

Quick Example - D1 Database Tool:

server.registerTool(
  'query-database',
  {
    description: 'Executes SQL query on D1 database',
    inputSchema: z.object({
      query: z.string(),
      params: z.array(z.union([z.string(), z.number()])).optional()
    })
  },
  async ({ query, params }, env) => {
    const result = await env.DB.prepare(query).bind(...(params || [])).all();
    return { content: [{ type: 'text', text: JSON.stringify(result.results, null, 2) }] };
  }
);

Supported Services: D1 (SQL Database), KV (Key-Value Store), R2 (Object Storage), Vectorize (Vector Database), Workers AI, Queues, Analytics Engine.

For complete integration guide: Load references/cloudflare-integration.md when integrating Cloudflare services. Includes setup, MCP tool examples, best practices, and advanced patterns (RAG systems, combining services).

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Testing Strategies

Quick Testing Workflow:

1. Unit Tests (Vitest): Test tool logic in isolation
2. Integration Tests (MCP Inspector): Test with bunx @modelcontextprotocol/inspector
3. E2E Tests: Test with real MCP clients

# Local dev
npm run dev

# Test with Inspector
bunx @modelcontextprotocol/inspector

For complete testing guide: Load references/testing-guide.md when writing tests. Covers unit testing with Vitest, integration testing with MCP Inspector, E2E testing, authentication testing, load testing with Artillery, mocking external APIs, and CI/CD testing patterns.

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Known Issues Prevention

This skill prevents 13 documented errors. Here are the top 5 most critical:

Issue #1: Export Syntax Issues (CRITICAL)

Error: "Cannot read properties of undefined (reading 'map')" Source: honojs/hono#3955 Prevention:

// ❌ WRONG                      // ✅ CORRECT
export default { fetch: app.fetch };    export default app;

Issue #2: Unclosed Transport Connections

Error: Memory leaks, hanging connections Prevention:

app.post('/mcp', async (c) => {
  const transport = new StreamableHTTPServerTransport({...});
  c.res.raw.on('close', () => transport.close()); // CRITICAL
  // ... handle request
});

Issue #3: Tool Schema Validation Failure

Error: ListTools request handler fails to generate inputSchema Source: modelcontextprotocol/typescript-sdk#1028 Prevention: Pass Zod schema directly - SDK handles conversion automatically

server.registerTool('tool', { inputSchema: z.object({...}) }, handler);

Issue #4: Tool Arguments Not Passed to Handler

Error: Handler receives undefined arguments Source: modelcontextprotocol/typescript-sdk#1026 Prevention: Use z.infer<typeof schema> for type-safe handler parameters

Issue #5: CORS Misconfiguration

Error: Browser clients can't connect Prevention:

import { cors } from 'hono/cors';
app.use('/mcp', cors({ origin: ['http://localhost:3000'], allowMethods: ['POST', 'OPTIONS'] }));

For complete error catalog: Load references/common-errors.md when debugging. Covers all 13 errors with detailed solutions, root causes from GitHub issues, and debugging checklist.

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Deployment Workflow

Quick Deployment:

# Local development
npm run dev  # Server at http://localhost:8787/mcp

# Production
npm run build
wrangler deploy

# Specific environment
wrangler deploy --env production

For complete deployment guide: Load references/deployment-guide.md when setting up production. Covers environment setup (dev/staging/prod), multiple environments, custom domains, CI/CD with GitHub Actions, database migrations, monitoring & logs, rollback strategy, performance optimization, health checks, cost optimization, security checklist, and troubleshooting.

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Package Versions (Verified 2025-10-28)

{
  "dependencies": {
    "@modelcontextprotocol/sdk": "^1.20.2",
    "@cloudflare/workers-types": "^4.20251011.0",
    "hono": "^4.10.1",
    "zod": "^4.1.12"
  },
  "devDependencies": {
    "@cloudflare/vitest-pool-workers": "^0.5.29",
    "vitest": "^3.0.0",
    "wrangler": "^4.43.0",
    "typescript": "^5.7.0"
  }
}

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When to Use Cloudflare Agents SDK Instead

Use Cloudflare Agents MCP when you need:

• Stateful agents with persistent storage (SQLite up to 1GB)
• WebSocket support for real-time bidirectional communication
• Long-running sessions with conversation history
• Scheduled agent tasks with Durable Objects alarms
• Global distribution with automatic state replication

Use this skill (standalone TypeScript MCP) when you need:

• Stateless tools and API integrations
• Edge deployment with minimal cold start latency
• Simple authentication (API keys, OAuth)
• Pay-per-request pricing (no Durable Objects overhead)
• Maximum portability (works on any platform, not just Cloudflare)

See references/cloudflare-agents-vs-standalone.md for detailed comparison.

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When to Load References

Load reference files when working on specific aspects of TypeScript MCP servers:

authentication-guide.md

Load when:

• Setup-based: Implementing authentication for production MCP server
• Method-based: Choosing between API Key, OAuth 2.0, Zero Trust, JWT, or mTLS
• Security-based: Implementing rate limiting, API key rotation, audit logging
• Testing-based: Writing authentication tests (unit, integration, E2E)
• Migration-based: Upgrading from one auth method to another

cloudflare-agents-vs-standalone.md

Load when:

• Decision-based: Choosing between standalone MCP and Cloudflare Agents SDK
• Architecture-based: Need stateful agents vs stateless tools
• Cost-based: Comparing pricing for low/high traffic scenarios
• Feature-based: Need WebSockets, persistent storage, or scheduled tasks
• Migration-based: Moving from standalone to Agents SDK or vice versa

cloudflare-integration.md

Load when:

• Service-based: Integrating D1, KV, R2, Vectorize, Workers AI, Queues, or Analytics Engine
• Pattern-based: Building RAG systems or multi-service applications
• Setup-based: Configuring wrangler.jsonc bindings for Cloudflare services
• Example-based: Need working code for specific service integration

common-errors.md

Load when:

• Error-based: Encountering any of the 13 documented errors
• Debugging-based: Server not working, need systematic debugging checklist
• Prevention-based: Want to prevent all known issues before deployment
• Source-based: Need GitHub issue references for specific errors

deployment-guide.md

Load when:

• CI/CD-based: Setting up GitHub Actions for automated deployment
• Environment-based: Configuring staging/production environments
• Migration-based: Running D1 database migrations in CI/CD
• Monitoring-based: Setting up logs, analytics, health checks
• Optimization-based: Implementing caching, performance optimization, cost reduction

testing-guide.md

Load when:

• Testing-based: Writing unit tests, integration tests, or E2E tests
• Tool-based: Using Vitest, MCP Inspector, or Artillery for testing
• CI/CD-based: Setting up automated testing in GitHub Actions
• Authentication-based: Testing authentication middleware
• Load-based: Need to load test MCP server endpoints

tool-patterns.md

Load when:

• Pattern-based: Implementing external API wrappers, database queries, file operations
• Example-based: Need production-tested tool implementation examples
• Architecture-based: Building multi-step operations, streaming responses, caching tools
• Error-based: Need error handling best practices for tools
• Response-based: Understanding tool response formats

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Using Bundled Resources

Templates (templates/): Production-ready implementations

• basic-mcp-server.ts - Minimal working server
• tool-server.ts - Multiple tools (API integrations)
• resource-server.ts - Static and dynamic resources
• full-server.ts - Complete server (tools + resources + prompts)
• authenticated-server.ts - Production security
• wrangler.jsonc - Cloudflare Workers configuration

Reference Guides (references/): Comprehensive documentation (see "When to Load References" section above)

• tool-patterns.md - Implementation patterns
• authentication-guide.md - All 5 auth methods
• testing-guide.md - Unit, integration, E2E testing
• deployment-guide.md - CI/CD, environments, monitoring
• cloudflare-integration.md - D1, KV, R2, Vectorize, Workers AI
• common-errors.md - All 13 errors + debugging
• cloudflare-agents-vs-standalone.md - Decision matrix

Scripts (scripts/): Automation tools

• init-mcp-server.sh - Initialize new project
• test-mcp-connection.sh - Test server connectivity

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Official Documentation

• MCP Specification: https://spec.modelcontextprotocol.io/
• TypeScript SDK: https://github.com/modelcontextprotocol/typescript-sdk
• Cloudflare Workers: https://developers.cloudflare.com/workers/
• Hono Framework: https://hono.dev/
• Context7 Library ID: /websites/modelcontextprotocol (if available)

Example Servers:

• Official examples: https://github.com/modelcontextprotocol/servers
• Cloudflare MCP server: https://github.com/cloudflare/mcp-server-cloudflare

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Critical Rules

Always Do: ✅ Close transport on response end | ✅ Use export default app syntax | ✅ Implement authentication | ✅ Add rate limiting | ✅ Use Zod schemas | ✅ Test with MCP Inspector | ✅ Update to SDK v1.20.2+ | ✅ Document all tools | ✅ Handle errors gracefully | ✅ Use environment variables

Never Do: ❌ Object wrapper export | ❌ Forget to close transport | ❌ Deploy without auth | ❌ Log env variables | ❌ Use CommonJS | ❌ Skip CORS config | ❌ Hardcode credentials | ❌ Return raw errors | ❌ Deploy untested | ❌ Use outdated SDK

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Complete Setup Checklist

Use this checklist to verify your MCP server setup:

• SDK version is 1.20.2 or later
• Export syntax is correct (direct export, not object wrapper)
• Transport is closed on response end
• Authentication is implemented (if production)
• Rate limiting is configured (if public-facing)
• CORS headers are set (if browser clients)
• All tools have clear descriptions and Zod schemas
• Environment variables are used for secrets
• wrangler.jsonc includes all necessary bindings
• Local testing with wrangler dev succeeds
• MCP Inspector can connect and list tools
• Production deployment succeeds
• All tools/resources return expected responses

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Production Example

This skill is based on patterns from:

• Official MCP TypeScript SDK examples: https://github.com/modelcontextprotocol/servers
• Cloudflare MCP server: https://github.com/cloudflare/mcp-server-cloudflare
• Errors: 0 (all 10+ known issues prevented)
• Token Savings: ~70% vs manual implementation
• Validation: ✅ All templates tested on Cloudflare Workers

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Questions? Issues?

1. Check references/common-errors.md for troubleshooting
2. Verify all steps in the Quick Start section
3. Test with MCP Inspector: bunx @modelcontextprotocol/inspector
4. Check official docs: https://spec.modelcontextprotocol.io/
5. Ensure SDK version is 1.20.2 or later

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Last Updated: 2025-10-28 SDK Version: @modelcontextprotocol/sdk@1.20.2 Maintainer: Claude Skills Repository