typescript-mcp

# TypeScript MCP on Cloudflare Workers

**Last Updated**: 2026-01-21
**Versions**: @modelcontextprotocol/sdk@1.25.3, hono@4.11.3, zod@4.3.5
**Spec Version**: 2025-11-25

---

## Quick Start

```bash
npm install @modelcontextprotocol/sdk@latest hono zod
npm install -D @cloudflare/workers-types wrangler typescript
```

**Transport Recommendation**: Use `StreamableHTTPServerTransport` for production. SSE transport is deprecated and maintained for backwards compatibility only. Streamable HTTP provides better error recovery, bidirectional communication, and simplified deployment.

**Basic MCP Server**:
```typescript
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' });

server.registerTool(
  'echo',
  {
    description: 'Echoes back input',
    inputSchema: z.object({ text: z.string() })
  },
  async ({ text }) => ({ content: [{ type: 'text', text }] })
);

const app = new Hono();

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

  // CRITICAL: Set error handler to catch transport errors
  transport.onerror = (error) => {
    console.error('MCP transport error:', error);
  };

  // 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; // CRITICAL: Direct export, not { fetch: app.fetch }
```

**Deploy**: `wrangler deploy`

---

## Authentication

**API Key** (KV-based):
```typescript
app.use('/mcp', async (c, next) => {
  const apiKey = c.req.header('Authorization')?.replace('Bearer ', '');
  const isValid = await c.env.M