Express.js Adapter

The Express adapter converts WebMCP's Web Standard HTTP transport into Express.js middleware.

Installation

bun add @thestudioxi/webmcp @thestudioxi/webmcp-adapter-express express

Usage

import express from 'express';
import { WebMCPServer, WebStandardHttpTransport } from '@thestudioxi/webmcp';
import { createExpressWebMCPMiddleware } from '@thestudioxi/webmcp-adapter-express';

// Create transport and server
const transport = new WebStandardHttpTransport();
const server = new WebMCPServer({ transport });

// Register tools
server.registerTool(
  {
    name: 'get_time',
    description: 'Get the current server time',
    inputSchema: { type: 'object', properties: {} },
  },
  async () => ({ time: new Date().toISOString() })
);

await server.start();

// Mount as Express middleware
const app = express();
app.use(express.json());
app.use('/api/webmcp', createExpressWebMCPMiddleware(transport));

app.listen(3000, () => {
  console.log('WebMCP Express server running on http://localhost:3000');
});

How It Works

createExpressWebMCPMiddleware() returns a standard Express middleware function (req, res, next) that:

1. Converts the Express req into a Web Standard Request
2. Passes it to WebStandardHttpTransport.handleRequest()
3. Converts the Web Standard Response back to Express res
4. Calls next(err) on errors for Express error handling

API

createExpressWebMCPMiddleware(transport)

Parameter	Type	Description
transport	WebStandardHttpTransport	Connected transport instance

Returns: Express middleware function (req, res, next) => void

TIP

Make sure to add express.json() middleware before the WebMCP middleware so that req.body is parsed.