stefanoauciello/mcp-server

MCP Server (demo-node-server)

1. What this project does

• This is a minimal MCP (Model Context Protocol) server written in Node.js.
• It exposes a tool called "add_numbers" that sums two numbers and returns:
  • Text output: "Result: "
  • Structured output (JSON): { "result": number }
• It is intended as a starting point for developing and registering custom MCP tools using @modelcontextprotocol/sdk with validation via zod.

2. How to use

Requirements

• Node.js 18 or newer
• npm (or pnpm/yarn if you prefer)

Installation

npm install

Run locally (STDIO)

# option 1
npm run server

# option 2
node server.js

If startup succeeds, you will see logs (stderr) like:

[demo-node-server] Starting, registering tools...
[demo-node-server] Ready (stdio connected)

Integrate with an MCP client (e.g., Claude Desktop)

• Add a new MCP server in the client settings with the following parameters:
  • command: node
  • args: ["server.js"]
  • cwd: path to this project folder (e.g., C:/Users/step1/Desktop/github/mcp-server on Windows)
• Restart or reload your MCP client to apply the configuration.

Available tools

• add_numbers
  • Input: { a: number, b: number }
  • Structured output: { result: number }
  • Text output: Result: <sum>

Example call (conceptual) Request:

{ "tool": "add_numbers", "params": { "a": 2, "b": 3 } }

Response (structured content):

{ "result": 5 }

Main project structure

• server.js: defines the MCP server, registers the add_numbers tool, and handles the STDIO transport.
• package.json: npm scripts (npm run server) and dependencies (@modelcontextprotocol/sdk, zod).
• launch.json: launch configuration (optional, for IDE/editor).

Troubleshooting

• Make sure you use Node 18+.
• If your MCP client doesn’t detect the server:
  • Verify that node server.js works from the terminal in the project folder.
  • Check that the client configuration cwd points to the correct folder.
  • Inspect stderr logs (prefixed with [demo-node-server]).