my-mcp

A small demonstration repository showing how to build Model Context Protocol (MCP) servers in Node.js using the @modelcontextprotocol/sdk package.

This project includes two example server scripts:

• mcp.js - a minimal MCP server exposing a simple addition tool.
• weather.js - an MCP server exposing a weather lookup tool using the Open-Meteo API.

Features

• mcp.js

  • Registers an add tool that accepts two numbers and returns their sum.
  • Demonstrates basic MCP server setup and tool registration.

• weather.js

  • Registers a get_weather tool that fetches current weather for a latitude/longitude pair.
  • Uses openmeteo and zod for API calls and input validation.
  • Returns both human-readable text and structured output.

Prerequisites

• Node.js 18+ installed
• Internet access for the weather example

Install

npm install

Usage

Run the addition server:

node mcp.js

Run the weather server:

node weather.js

Each script starts an MCP server using StdioServerTransport, so it expects MCP-compatible client communication over standard input/output.

File Overview

• mcp.js - MCP server example registering an add tool.
• weather.js - MCP server example registering a get_weather tool.
• package.json - project metadata and dependencies.

Dependencies

• @modelcontextprotocol/sdk - MCP server SDK
• openmeteo - helper for Open-Meteo weather API requests
• zod - runtime schema validation

Notes

• The weather.js example uses Open-Meteo query parameters to request current weather variables.
• The example returns structured data for temperature, humidity, wind, precipitation, and day/night state.

Extending this project

• Add more MCP tools to either server.
• Add a client implementation to send MCP requests and receive tool results.
• Replace the default StdioServerTransport with another transport for different integration patterns.