Express

Deploy your MCP server over HTTP using Express.

Install

pnpm

pnpm add @lynq/lynq @lynq/express zod express

npm

npm install @lynq/lynq @lynq/express zod express

yarn

yarn add @lynq/lynq @lynq/express zod express

bun

bun add @lynq/lynq @lynq/express zod express

Usage

import express from "express";
import { createMCPServer } from "@lynq/lynq";
import { mountLynq } from "@lynq/express";
import { z } from "zod";

const server = createMCPServer({ name: "my-server", version: "1.0.0" });

server.tool(
  "add",
  {
    description: "Add two numbers",
    input: z.object({ a: z.number(), b: z.number() }),
  },
  (args, c) => c.text(String(args.a + args.b)),
);

const app = express();
app.use(express.json());
mountLynq(app, server);

app.listen(3000);

Note: Express must have a JSON body parser registered before mountLynq. The adapter re-serializes req.body into a Web Standard Request, so the body must already be parsed.

Under the hood

The Express adapter converts Express req/res objects into a Web Standard Request, passes it to server.http(), then streams the Response back. This means Express is a thin wrapper -- the real MCP logic uses the same Web Standard handler as Hono, Deno, and every other runtime.

Options

mountLynq(app, server, {
  // Route path (default: "/mcp")
  path: "/mcp",

  // Override allowed hostnames for Host header validation
  allowedHosts: ["localhost", "127.0.0.1", "::1"],
});

path

The route path where the MCP endpoint is mounted. Defaults to "/mcp".

allowedHosts

Array of hostnames accepted in the Host header. Defaults to ["localhost", "127.0.0.1", "::1"]. Set to your production domain when deploying publicly.

Pages

Auto-register OAuth callback and payment page routes. Same API as the Hono adapter:

mountLynq(app, server, {
  pages: {
    github: {
      clientId: process.env.GITHUB_CLIENT_ID!,
      clientSecret: process.env.GITHUB_CLIENT_SECRET!,
    },
    crypto: true,
  },
});

Note: The crypto payment POST callback requires express.json() middleware, which must be registered before mountLynq.

See Hono — Pages for the full provider config table and pagesPrefix option.

Next Steps

• HTTP -- raw server.http() API, runtime examples
• Hono -- Hono adapter
• Transports -- stateful vs sessionless
• Claude Code -- connect Claude Code to your HTTP server