Weather MCP Server

Instructions

Implementation Reference

• src/index.js:240-290 (handler)

  The primary handler function for the get_weather_forecast tool. It geocodes the city (using helper), fetches daily forecast data from Open-Meteo API, formats it into a structured text response with temperatures, conditions, wind, sunrise/sunset for each day.

  async getWeatherForecast(city, country, days) {
    let location;
    
    if (city.toLowerCase() === 'sydney' && !country) {
      location = DEFAULT_LOCATION;
    } else {
      location = await this.getCoordinates(city, country);
    }
  
    const url = `${WEATHER_API}?latitude=${location.latitude}&longitude=${location.longitude}&daily=weather_code,temperature_2m_max,temperature_2m_min,apparent_temperature_max,apparent_temperature_min,sunrise,sunset,precipitation_sum,rain_sum,showers_sum,snowfall_sum,precipitation_hours,wind_speed_10m_max,wind_gusts_10m_max,wind_direction_10m_dominant&timezone=auto&forecast_days=${days}`;
    
    const response = await fetch(url);
    const data = await response.json();
  
    if (!response.ok) {
      throw new Error('Erreur lors de la récupération des prévisions');
    }
  
    const daily = data.daily;
    let forecastText = `🗓️ Prévisions météo ${days} jours pour ${location.name || location.admin1}${location.country ? `, ${location.country}` : ''}\n\n`;
    
    for (let i = 0; i < days; i++) {
      const date = new Date(daily.time[i]);
      const dayName = date.toLocaleDateString('fr-FR', { weekday: 'long' });
      const dateStr = date.toLocaleDateString('fr-FR');
      const weatherDesc = this.getWeatherDescription(daily.weather_code[i]);
      const windDir = this.getWindDirection(daily.wind_direction_10m_dominant[i]);
      
      forecastText += `📅 **${dayName.charAt(0).toUpperCase() + dayName.slice(1)} ${dateStr}**\n`;
      forecastText += `🌡️ ${Math.round(daily.temperature_2m_min[i])}°C → ${Math.round(daily.temperature_2m_max[i])}°C\n`;
      forecastText += `🤔 Ressenti: ${Math.round(daily.apparent_temperature_min[i])}°C → ${Math.round(daily.apparent_temperature_max[i])}°C\n`;
      forecastText += `☁️ ${weatherDesc}\n`;
      forecastText += `🌬️ Vent: ${Math.round(daily.wind_speed_10m_max[i])} km/h ${windDir}\n`;
      
      if (daily.precipitation_sum[i] > 0) {
        forecastText += `🌧️ Précipitations: ${daily.precipitation_sum[i]}mm\n`;
      }
      
      forecastText += `🌅 Lever: ${new Date(daily.sunrise[i]).toLocaleTimeString('fr-FR', {hour: '2-digit', minute: '2-digit'})}\n`;
      forecastText += `🌇 Coucher: ${new Date(daily.sunset[i]).toLocaleTimeString('fr-FR', {hour: '2-digit', minute: '2-digit'})}\n\n`;
    }
  
    return {
      content: [
        {
          type: 'text',
          text: forecastText.trim(),
        },
      ],
    };
  }

• src/index.js:70-95 (schema)

  Tool schema definition in the ListTools response, specifying name, description, and input schema with optional parameters city, country, and days.

  {
    name: 'get_weather_forecast',
    description: 'Récupère les prévisions météo sur 7 jours (Sydney par défaut)',
    inputSchema: {
      type: 'object',
      properties: {
        city: {
          type: 'string',
          description: 'Nom de la ville (optionnel, Sydney par défaut)',
          default: 'Sydney'
        },
        country: {
          type: 'string',
          description: 'Code pays optionnel',
        },
        days: {
          type: 'number',
          description: 'Nombre de jours de prévision (1-7)',
          default: 7,
          minimum: 1,
          maximum: 7
        }
      },
      required: [],
    },
  },

• src/index.js:149-150 (registration)

  Registration in the CallToolRequestSchema switch statement that dispatches to the getWeatherForecast handler with default parameters.

  case 'get_weather_forecast':
    return await this.getWeatherForecast(args.city || 'Sydney', args.country, args.days || 7);

• src/index.js:178-190 (helper)

  Helper function used by the handler to resolve city/country to latitude/longitude coordinates via Open-Meteo geocoding API.

  async getCoordinates(city, country) {
    const query = country ? `${city}, ${country}` : city;
    const url = `${GEOCODING_API}?name=${encodeURIComponent(query)}&count=1&language=fr&format=json`;
    
    const response = await fetch(url);
    const data = await response.json();
  
    if (!response.ok || !data.results || data.results.length === 0) {
      throw new Error(`Ville "${query}" non trouvée`);
    }
  
    return data.results[0];
  }

• src/index.js:395-428 (helper)

  Helper utility to translate weather codes to human-readable French descriptions, used in forecast formatting.

  getWeatherDescription(code) {
    const descriptions = {
      0: 'Ciel dégagé',
      1: 'Principalement dégagé',
      2: 'Partiellement nuageux',
      3: 'Couvert',
      45: 'Brouillard',
      48: 'Brouillard givrant',
      51: 'Bruine légère',
      53: 'Bruine modérée',
      55: 'Bruine dense',
      56: 'Bruine verglaçante légère',
      57: 'Bruine verglaçante dense',
      61: 'Pluie légère',
      63: 'Pluie modérée',
      65: 'Pluie forte',
      66: 'Pluie verglaçante légère',
      67: 'Pluie verglaçante forte',
      71: 'Neige légère',
      73: 'Neige modérée',
      75: 'Neige forte',
      77: 'Grains de neige',
      80: 'Averses légères',
      81: 'Averses modérées',
      82: 'Averses violentes',
      85: 'Averses de neige légères',
      86: 'Averses de neige fortes',
      95: 'Orage',
      96: 'Orage avec grêle légère',
      99: 'Orage avec grêle forte'
    };
    
    return descriptions[code] || 'Conditions inconnues';
  }