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MCP Middleware Adapter for Express Servers

@Moe03

Repository

About MCP Middleware Adapter for Express Servers

Run multiple MCP clients on a NodeJS Express server (adapter/middleware)

#nodejs#adapter#middleware#express#mcp

Basic information

Category

Developer Tools

License

MIT

Runtime

node

Transports

stdio

Publisher

Moe03

Config

Add this server to your MCP-compatible client using the configuration below.

{
  "mcpServers": {
    "mcp-express-adapter": {
      "command": "npx",
      "args": [
        "mcp-express-adapter@latest",
        "--host",
        "http://localhost:3000/mcp/sse",
        "--header",
        "Authorization: Bearer 000000"
      ]
    }
  }
}

Tools

No tools detected

We auto-extract tools from the README. The maintainer can list them under a ## Tools heading to populate this section.

Overview

What is MCP Middleware Adapter for Express Servers?

It is a lightweight adapter that creates MCP (Model Context Protocol) servers using Express.js, allowing developers to host and serve MCP tools via SSE (Server-Sent Events) on an Express server. It targets developers who need to deploy, scale, and maintain multiple MCP clients efficiently.

How to use MCP Middleware Adapter for Express Servers?

Install via npm with npm install mcp-express-adapter@latest. Then define tools using the mcpTool helper with Zod schemas, create an MCPClient with an endpoint and tools, mount its middleware on an Express app, and connect to the SSE endpoint (e.g., http://localhost:3000/mcp/sse). To test with Claude Desktop, configure mcpServers using npx -y mcp-express-adapter --host <url>.

Key features of MCP Middleware Adapter for Express Servers

  • Express middleware integration with SSE transport
  • TypeScript‑friendly tool definition using Zod schemas
  • Header‑based authorization support
  • Multiple MCP clients on different endpoints
  • Lightweight design for deploying and scaling MCP servers
  • Simplifies hosting many MCP tools in one process

Use cases of MCP Middleware Adapter for Express Servers

  • Host weather, calculator, and time tools on separate Express endpoints
  • Combine lightweight MCP servers to avoid running many separate processes
  • Integrate MCP tools with LangChain agents via @langchain/mcp-adapters
  • Serve MCP tools to Claude Desktop or other MCP‑compatible clients
  • Scale MCP tools without spawning individual npx sessions for each user

FAQ from MCP Middleware Adapter for Express Servers

How do I install MCP Middleware Adapter for Express Servers?

Install it using npm, yarn, or pnpm: npm install mcp-express-adapter@latest. Note that if installing from a private GitHub Packages registry, you must authenticate.

Does it support WebSocket transport?

Currently only SSE (Server‑Sent Events) is implemented and working. WebSocket support is planned but not yet available.

Can I host multiple MCP clients on the same Express server?

Yes, you can create multiple MCPClient instances, each with a different endpoint (e.g., /weather-mcp, /calculator-mcp), and mount their middleware separately.

How

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