Hello World MCP Server

A simple Model Context Protocol (MCP) server implementation built with TypeScript. This server demonstrates basic MCP functionality including resources, prompts, and tools.

Features

- SSE and STDIO transport support
- Resource handling with static and dynamic resources
- Sample prompt implementation
- Example tool that echoes messages
- Debug tool for server introspection

Getting Started

Prerequisites

- Node.js (v16 or higher)
- npm or yarn

Installation

npm install

Build

npm run build

Running the Server

HTTP/SSE Transport (Web Browsers)

npm run start:http

This starts the server on http://localhost:3000 with:
- SSE endpoint at /sse
- Message endpoint at /messages

STDIO Transport (Command Line)

npm run start

This runs the server in stdio mode for command-line integrations.

Testing the Server

Testing with cURL

1. Start the HTTP server:

   npm run start:http

   

2. In a terminal window, connect to the SSE endpoint:

   curl -N http://localhost:3000/sse

   

   event: endpoint

   data: /messages?sessionId=YOUR_SESSION_ID

   

3. In another terminal window, send a request to invoke the echo tool:

   curl -X POST \

     "http://localhost:3000/messages?sessionId=YOUR_SESSION_ID" \

     -H 'Content-Type: application/json' \

     -d '{

       "jsonrpc": "2.0",

       "id": 1,

       "method": "tools/invoke",

       "params": {

         "name": "echo",

         "parameters": {

           "message": "Testing the MCP server!"

         }

       }

     }'

   

4. You should see a response in the SSE terminal window:

   event: message

   data: {"jsonrpc":"2.0","id":1,"result":{"content":[{"type":"text","text":"Hello Testing the MCP server!"}]}}

   

5. Try the debug tool to see available server methods:

   curl -X POST \

     "http://localhost:3000/messages?sessionId=YOUR_SESSION_ID" \

     -H 'Content-Type: application/json' \

     -d '{

       "jsonrpc": "2.0",

       "id": 2,

       "method": "tools/invoke",

       "params": {

         "name": "debug",

         "parameters": {}

       }

     }'

   

Testing with MCP Inspector

For a visual interface, you can use the MCP Inspector tool:

1. Connect to http://localhost:3000/sse in the MCP Inspector
2. Browse available resources and tools
3. Invoke tools interactively

Server API

Resources

- hello://world - A static hello world resource
- greeting://{name} - A dynamic greeting with a name parameter

Tools

- echo - Echoes back a message with "Hello" prefix
- debug - Lists all available tools and methods

Prompts

- helpful-assistant - A basic helpful assistant prompt

Troubleshooting

- If you get "Headers already sent" errors, make sure you're not manually setting headers
- Session ID handling is crucial for proper message routing
- Check the server console for debugging information

License

MIT