🌤️ MCP Weather Server

A production-grade Model Context Protocol (MCP) server providing comprehensive real-time weather data using the free Open-Meteo API.

✨ Features

🌦️ Weather Data

• Current Weather: Real-time conditions with 20+ meteorological parameters

• 5-Day Forecast: Detailed daily predictions with solar, UV, and precipitation data

• Comprehensive Metrics: Temperature, humidity, wind, pressure, UV index, visibility, cloud cover

• Solar Data: Sunshine duration, daylight hours, solar radiation, evapotranspiration

🚀 Performance & Reliability

• Redis Caching: Intelligent caching with configurable TTL (15min current, 1h forecast)

• Metrics & Monitoring: Real-time performance tracking and error logging

• Graceful Degradation: Continues working without Redis/cache if unavailable

• Type-Safe: Full Zod validation for all inputs and API responses

🏗️ Architecture

• Multiple Transports: Stdio (MCP Inspector) + HTTP/SSE streaming

• Factory Pattern: Isolated server instances per session

• Layered Design: Services, Tools, Server separation

• ESM Modules: Modern JavaScript with full ES2022 support

🔧 Developer Experience

• 64 Unit Tests: Comprehensive Jest test suite

• Hot Reload: Development mode with file watching

• Debug Support: Integrated debugging for both transports

• Rich Logging: Structured logs with performance metrics

📊 Data Sources

Open-Meteo API (Free Tier)

• No API Key Required - Unlimited calls for non-commercial use

• Global Coverage - Weather models for every location worldwide

• Multiple Models - ECMWF, NOAA GFS, Météo-France, DWD ICON, and more

• Real-time Updates - 15-minute to hourly resolution

Available Weather Variables

Current Conditions

• Temperature & "Feels Like" (2m & apparent)

• Humidity, Dew Point, Vapour Pressure Deficit

• Wind Speed/Direction/Gusts (10m, 80m, 120m, 180m altitudes)

• Pressure (MSL & Surface), Cloud Cover (Total/Low/Mid/High)

• Visibility, UV Index, Precipitation

• Evapotranspiration & Reference ET₀

Forecast Data

• Daily min/max temperatures (actual & apparent)

• Precipitation (total, rain, showers, snow)

• Wind (speed, gusts, dominant direction)

• Solar (sunrise/sunset, sunshine/daylight duration, UV index)

• Radiation (shortwave solar radiation sum)

🏛️ Architecture

src/
├── index.js                    # Entry point & transport orchestration
├── server/
│   ├── weatherMcpFactory.js    # Server factory with cache init
│   └── streamableHttpServer.js # HTTP/SSE transport server
├── services/
│   ├── weatherApi.js          # Open-Meteo API client with caching
│   ├── weatherCodes.js        # WMO weather code mappings
│   ├── cache.js               # Redis cache service
│   └── metrics.js             # Performance monitoring
└── tools/
    ├── schemas.js             # Zod validation schemas
    ├── getWeatherTool.js      # Current weather MCP tool
    ├── getWeatherForecast5DaysTool.js # Forecast MCP tool
    └── getServerStatsTool.js  # Server metrics tool

Design Patterns

📋 Installation

Prerequisites

• Node.js ≥16.0.0 (with --experimental-vm-modules for Jest)

• Redis (optional, for caching) - Install from redis.io

Setup

# Clone repository
git clone <repository-url>
cd mcp-weather

# Install dependencies
npm install

# Run tests
npm test

# Start server (stdio mode)
npm start

Environment Variables

# Redis configuration (optional)
REDIS_URL=redis://localhost:6379

# HTTP server configuration
MCP_HTTP_PORT=3333
MCP_HTTP_HOST=127.0.0.1

🚀 Usage

MCP Inspector (Recommended)

# Start in stdio mode for MCP Inspector
npm start

# Then open MCP Inspector and connect to the server

HTTP/SSE Mode

# Start HTTP server with SSE transport
npm run start:http

# Server runs on http://127.0.0.1:3333
# MCP endpoint: http://127.0.0.1:3333/mcp

Development Mode

# With hot reload
npm run dev

# With debugging
npm run debug:http  # HTTP mode
npm run debug       # Stdio mode

🔧 API Reference

Tools

get_weather

Get current weather conditions for coordinates.

Input:

{
  "latitude": 48.8566,
  "longitude": 2.3522
}

Output:

🌤️ Current Weather

📍 Location: 48.8566, 2.3522
🌡️ Temperature: 22.5°C (feels like 24.1°C)
💧 Humidity: 65%
🌫️ Dew Point: 15.8°C
💨 Wind: 12 km/h from WSW
🌪️ Wind Gusts: 18 km/h
☁️ Conditions: Partly cloudy
☁️ Cloud Cover: 45% (Low: 20%, Mid: 15%, High: 10%)
👁️ Visibility: 24 km
🧭 Pressure: 1013 hPa (MSL) / 1011 hPa (Surface)
☀️ UV Index: 6
💧 Evapotranspiration: 0.15 mm/h
🌱 Reference ET₀: 0.22 mm/h
🌡️ Vapor Pressure Deficit: 0.85 kPa
🌍 Timezone: Europe/Paris
🕐 Updated: 2024-03-29T14:30:00Z

get_weather_forecast

Get 5-day weather forecast for coordinates.

Input:

{
  "latitude": 48.8566,
  "longitude": 2.3522
}

Output:

📅 5-Day Forecast

📍 Coordinates : 48.8566, 2.3522
🌍 Timezone    : Europe/Paris

📅 2024-03-29
   🌡️  18°C – 24°C (feels 16°C – 26°C)
   ☁️  Partly cloudy
   💧 Precipitation: 0.2 mm (0 rain + 0.1 showers + 0 snow)
   🌧️ Chance: 15% over 0.5h
   🌅 Sunrise: 06:45 | Sunset: 19:32
   ☀️  Sunshine: 8.2h / Daylight: 12.8h
   ☀️  UV Index: 6 (Clear sky: 7)
   💨 Wind: 15 km/h gusts to 22 km/h from W
   ⚡ Solar Radiation: 18.5 MJ/m²
   🌱 Reference ET₀: 4.2 mm

get_server_stats

Get server performance metrics and cache statistics.

Input: (no parameters required)

Output:

📊 Server Statistics

⏱️  Uptime: 45 minutes
🔄 API Calls: 127
💾 Cache Hits: 89 (70.1%)
❌ Errors: 2
⚡ Avg Response Time: 245ms

🔧 Tool Usage:
   • get_weather: 95 calls
   • get_weather_forecast: 32 calls

📋 Cache Status:
   • Connected: ✅
   • Keys: 23
   • Memory: 2.4MB

🧪 Testing

Run Test Suite

# Run all tests
npm test

# Run with coverage
npm run test:coverage

# Run in watch mode
npm run test:watch

Test Architecture

• 64 unit tests covering all services and server components

• Mocked API calls for reliable testing without network dependencies

• Cache testing with Redis mock

• Schema validation testing with Zod

• Error handling coverage

Test Files

tests/
├── services/
│   ├── weatherApi.test.js     # API client tests
│   └── weatherCodes.test.js   # Weather code mapping tests
└── server/
    └── weatherMcpFactory.test.js # Server factory tests

📈 Monitoring & Metrics

Built-in Metrics

• API Call Tracking: Count, response times, cache hit rates

• Tool Usage: Per-tool invocation counts

• Error Tracking: Error types and frequencies

• Cache Performance: Hit rates, memory usage, connection status

• Server Health: Uptime, active sessions

Logs

Structured logging with:

• Request/response timing

• Cache operations

• API call details

• Error context

• Performance metrics

Cache Configuration

// Current weather: 15 minutes TTL
// Forecasts: 1 hour TTL
// Automatic expiration and cleanup

🔒 Security & Reliability

Data Validation

• Zod schemas for all inputs

• Coordinate bounds checking (-90/+90, -180/+180)

• API response validation

• Error sanitization (no sensitive data leakage)

Error Handling

• Graceful degradation (continues without cache)

• Structured error responses with appropriate HTTP codes

• Timeout handling for API calls

• Connection retry logic for Redis

Performance

• Connection pooling for Redis

• Request deduplication via caching

• Memory-efficient data structures

• Background cleanup of expired cache entries

🤝 Contributing

Development Setup

# Install dependencies
npm install

# Run tests
npm test

# Start development server
npm run dev

# Debug mode
npm run debug

Code Quality

• ESLint configuration for code style

• Prettier for consistent formatting

• Jest for comprehensive testing

• TypeScript definitions for better IDE support

Architecture Guidelines

• Layer separation: Services, Tools, Server layers

• Dependency injection: Injectable fetch/cache for testing

• Error boundaries: Comprehensive error handling

• Logging standards: Structured logging throughout

📄 License

MIT License - Free for personal and commercial use.

Open-Meteo Terms

• Non-commercial use: Unlimited API calls

• Commercial use: Contact Open-Meteo for licensing

• Attribution required for public deployments

🙏 Acknowledgments

• Open-Meteo for providing free, high-quality weather data

• Anthropic for the Model Context Protocol specification

• Weather model providers: ECMWF, NOAA, Météo-France, DWD, and others

📞 Support

Issues & Bugs

• GitHub Issues: Report bugs and request features

• Documentation: Check this README first

Community

• MCP Discord: Join the Model Context Protocol community

• Open-Meteo Forum: Weather API discussions

Built with ❤️ using the Model Context Protocol

Stdio Mode (Default)

npm start
# or: node src/index.js

Perfect for direct MCP client integration (Claude Desktop, IDEs, etc.)

HTTP/SSE Mode

# Via CLI flag
npm run start:http
# or: node src/index.js --http

# Via environment variables
TRANSPORT=http PORT=8080 node src/index.js

# Default HTTP port: 3001

HTTP Endpoints:

• GET /health - Health check endpoint

• GET /sse - Server-Sent Events stream

• POST /messages - Tool request endpoint

Demo Script

node demo.js

Shows real-world example calls to weather service for multiple cities.

Run Tests

npm test

Validates input schemas and weather code mappings.

🛠️ Available Tools

Tool: get_weather

Get current weather for a location.

Parameters:

{
  "latitude": -90 to 90,
  "longitude": -180 to 180
}

Example:

# Request current weather for Paris
{
  "latitude": 48.8566,
  "longitude": 2.3522
}

Response Example:

☀️ **CURRENT WEATHER**

📍 Location: 48.8566°N, 2.3522°E
🌡️  Temperature: 15°C
☁️  Condition: Partly cloudy
💧 Humidity: 65%
💨 Wind Speed: 12 km/h
🕐 Time: 2024-03-29T10:30:00Z
🌍 Timezone: Europe/Paris

Tool: get_forecast

Get 5-day weather forecast.

Parameters:

{
  "latitude": -90 to 90,
  "longitude": -180 to 180
}

Response Example:

📅 **5-DAY WEATHER FORECAST**

📍 Location: 48.8566°N, 2.3522°E
🌍 Timezone: Europe/Paris

**Day 1** - 2024-03-29
☁️ Partly cloudy
🔺 Max: 18°C | 🔻 Min: 12°C

**Day 2** - 2024-03-30
🌧️ Slight rain
🔺 Max: 16°C | 🔻 Min: 10°C

...

🌍 Popular Coordinates

🔗 Data Source

• API: Open-Meteo - Free, open-source weather API

• Documentation: https://open-meteo.com/en/docs

• Weather Codes: WMO Weather Interpretation Codes

📦 Module System

Uses ES Modules (ESM) with "type": "module" for modern JavaScript features:

• Clean import/export syntax

• Top-level await support

• Better tree-shaking compatibility

🧪 Testing

npm test

Test Coverage:

• Input coordinate validation (bounds checking)

• Weather code mapping (WMO codes)

• Schema validation with Zod

• Edge cases and error handling

📝 Project Structure

MCP-Weather/
├── src/
│   ├── index.js           # Main entry point
│   ├── server.js          # MCP server factory
│   ├── weatherService.js  # Weather API service
│   └── weatherTools.js    # MCP tools
├── package.json
├── demo.js                # Demo script
├── test.js                # Test suite
├── README.md
└── .env.example

🔧 Environment Variables

Example:

# Run in HTTP mode on custom port
TRANSPORT=http PORT=8080 npm start

🐛 Troubleshooting

📜 License

ISC

🤝 Contributing

This project follows the MCP specification and best practices for Node.js server development.