Express MCP Server

Express MCP Server

A stateless Model Context Protocol (MCP) server built with Express and TypeScript.

Features

• Stateless MCP server implementation with modern Streamable HTTP transport
• TypeScript for type safety
• Express.js for HTTP handling

Requirements

• Node.js 18+
• npm or yarn

Installation

# Clone the repository (or download)
git clone https://github.com/your-username/sample-express-mcp-server.git
cd sample-express-mcp-server

# Install dependencies
npm install

Development

# Build the TypeScript code
npm run build

# Run in development mode with auto-reloading
npm run dev

# Run tests (when added)
npm test

Server Structure

src/
  ├── index.ts                # Main application entry point
  └── server.ts               # MCP server definition with resource, tool, and prompt

Available Functionality

This server implements a simple echo endpoint with three MCP components:

• Resource: echo://{message} - Returns the message as a resource
• Tool: echo - Echoes the provided message back as a tool response
• Prompt: echo - Creates a user prompt with the provided message

MCP Protocol

This server implements the Model Context Protocol (MCP), a standardized way for LLMs to interact with external data and functionality. It exposes a stateless API endpoint that responds to JSON-RPC requests.

API Usage

Send a POST request to /mcp with a JSON-RPC payload:

Initialize

curl -X POST http://localhost:3001/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json" \
  -H "Accept: text/event-stream" \
  -d '{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "initialize",
    "params": {
      "protocolVersion": "2024-11-05",
      "capabilities": {
        "roots": {
          "listChanged": true
        },
        "sampling": {}
      },
      "clientInfo": {
        "name": "ExampleClient",
        "version": "1.0.0"
      }
    }
  }'

Call Echo Tool

curl -X POST http://localhost:3001/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json" \
  -H "Accept: text/event-stream" \
  -d '{
    "jsonrpc": "2.0",
    "method": "tools/call",
    "params": {
      "name": "echo",
      "arguments": {
        "message": "Hello, World!"
      }
    },
    "id": 1
  }'

License

ISC