学会这一招，任何API都能变成Claude Code的工具——MCP Server开发实战

你：北京现在天气怎么样？
Claude Code：[调用天气工具]
→ 北京当前温度 22.3°C，体感 22.5°C，湿度 59%，大部晴朗

你：那上海呢？未来三天会下雨吗？
Claude Code：[调用预报工具]
→ 上海未来三天都是晴天，27-28°C，降雨概率很低

Open-Meteo API（天气数据源）
        ↓
  MCP Server（把 API "翻译"成 AI 能调用的工具）
        ↓
  配置接入 Claude Code
        ↓
  AI 对话中自动查天气

// 直接复制到浏览器控制台就能看到结果
fetch('https://api.open-meteo.com/v1/forecast?latitude=39.9042&longitude=116.4074&current=temperature_2m&timezone=auto')
  .then(r => r.json())
  .then(d => console.log('北京当前温度:', d.current.temperature_2m + '°C'))

mkdir weather-mcp-server
cd weather-mcp-server
npm init -y
npm install @modelcontextprotocol/sdk zod
npm install -D typescript @types/node

{
  "compilerOptions": {
    "target": "ES2022",
    "module": "Node16",
    "moduleResolution": "Node16",
    "outDir": "./dist",
    "rootDir": "./src",
    "strict": true
  },
  "include": ["src"]
}

import { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
import { StdioServerTransport } from "@modelcontextprotocol/sdk/server/stdio.js";
import { z } from "zod";

// ── 基础配置 ──
const GEOCODING_BASE = "https://geocoding-api.open-meteo.com/v1";
const FORECAST_BASE = "https://api.open-meteo.com";

// ── 城市名 → 坐标 ──
async function geocode(city: string) {
  const url = `${GEOCODING_BASE}/search?name=${encodeURIComponent(city)}&count=3&language=zh&format=json`;
  const res = await fetch(url);
  if (!res.ok) return null;
  const data = await res.json() as { results?: Array<{ name: string; latitude: number; longitude: number; country: string; admin1?: string }> };
  return data.results?.[0] ?? null;
}

// ── 创建 Server ──
const server = new McpServer(
  { name: "weather-server", version: "1.0.0" },
  {
    capabilities: {},
    instructions: "使用此服务器查询天气信息。先调用 geocode 将城市名转为坐标，再调用天气工具获取天气数据。"
  }
);

// ── Tool 1：城市名转坐标 ──
server.registerTool(
  "geocode",
  {
    description: "将城市名称转换为经纬度坐标",
    inputSchema: z.object({
      city: z.string().describe("城市名称，如'北京'、'上海'")
    })
  },
  async ({ city }) => {
    const result = await geocode(city);
    if (!result) return { content: [{ type: "text", text: `未找到城市：${city}` }] };
    const region = result.admin1 ? `${result.country} ${result.admin1}` : result.country;
    return { content: [{ type: "text", text: `${result.name}：纬度 ${result.latitude}，经度 ${result.longitude}（${region}）` }] };
  }
);

// ── Tool 2：查询当前天气 ──
server.registerTool(
  "get_current_weather",
  {
    description: "查询指定城市当前的天气情况",
    inputSchema: z.object({
      city: z.string().describe("城市名称，如'北京'、'上海'")
    })
  },
  async ({ city }) => {
    const geo = await geocode(city);
    if (!geo) return { content: [{ type: "text", text: `未找到城市：${city}` }] };

    const url = `${FORECAST_BASE}/v1/forecast?latitude=${geo.latitude}&longitude=${geo.longitude}&current=temperature_2m,relative_humidity_2m,apparent_temperature,weather_code,wind_speed_10m&timezone=auto`;
    const res = await fetch(url);
    const data = await res.json() as { current?: Record<string, number> };

    const c = data.current;
    if (!c) return { content: [{ type: "text", text: `未能获取 ${city} 的天气数据` }] };

    const weatherMap: Record<number, string> = {
      0: "☀️ 晴天", 1: "🌤 大部晴朗", 2: "⛅ 多云", 3: "☁️ 阴天",
      45: "🌫 有雾", 51: "🌧 小毛毛雨", 61: "🌧 小雨", 63: "🌧 中雨",
      65: "🌧 大雨", 71: "❄️ 小雪", 73: "❄️ 中雪", 75: "❄️ 大雪",
      80: "🌧 阵雨", 95: "⛈️ 雷暴", 96: "⛈️ 冰雹雷暴", 99: "⛈️ 大冰雹雷暴"
    };

    return {
      content: [{
        type: "text",
        text: [
          `${geo.name} 当前天气：`,
          `  🌡 温度：${c.temperature_2m}°C（体感 ${c.apparent_temperature}°C）`,
          `  💧 湿度：${c.relative_humidity_2m}%`,
          `  🌬 风速：${c.wind_speed_10m} km/h`,
          `  ☁ 天气：${weatherMap[c.weather_code] || `代码 ${c.weather_code}`}`
        ].join("\n")
      }]
    };
  }
);

// ── Tool 3：天气预报 ──
server.registerTool(
  "get_weather_forecast",
  {
    description: "查询指定城市未来几天的天气预报",
    inputSchema: z.object({
      city: z.string().describe("城市名称"),
      days: z.number().default(3).describe("预报天数，1-7")
    })
  },
  async ({ city, days }) => {
    const geo = await geocode(city);
    if (!geo) return { content: [{ type: "text", text: `未找到城市：${city}` }] };

    const d = Math.min(Math.max(days ?? 3, 1), 7);
    const url = `${FORECAST_BASE}/v1/forecast?latitude=${geo.latitude}&longitude=${geo.longitude}&daily=temperature_2m_max,temperature_2m_min,precipitation_probability_max,weather_code&timezone=auto&forecast_days=${d}`;
    const res = await fetch(url);
    const data = await res.json() as { daily?: { time: string[]; temperature_2m_max: number[]; temperature_2m_min: number[]; precipitation_probability_max: number[]; weather_code: number[] } };

    if (!data.daily) return { content: [{ type: "text", text: `未能获取 ${city} 的预报数据` }] };

    const weatherSimple = (code: number): string => {
      if (code <= 3) return "晴";
      if (code <= 48) return "雾/霾";
      if (code <= 67) return "雨";
      if (code <= 77) return "雪";
      if (code <= 82) return "阵雨";
      if (code <= 86) return "阵雪";
      return "雷暴";
    };

    const lines = [`${geo.name} 未来 ${d} 天天气预报：`];
    for (let i = 0; i < d; i++) {
      const icon = data.daily.precipitation_probability_max[i] > 50 ? "🌧" : "☀";
      lines.push(`  ${data.daily.time[i]} ${icon} ${weatherSimple(data.daily.weather_code[i])} | 高温 ${data.daily.temperature_2m_max[i]}°C / 低温 ${data.daily.temperature_2m_min[i]}°C | 降雨概率 ${data.daily.precipitation_probability_max[i]}%`);
    }

    return { content: [{ type: "text", text: lines.join("\n") }] };
  }
);

// ── 启动 ──
async function main() {
  const transport = new StdioServerTransport();
  await server.connect(transport);
  console.error("Weather MCP Server running on stdio");
}

main().catch((err) => {
  console.error("启动失败:", err);
  process.exit(1);
});

# 构建
npx tsc

# 快速验证：手动发送一个初始化请求
printf '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test","version":"1.0"}}}\n{"jsonrpc":"2.0","method":"notifications/initialized"}\n{"jsonrpc":"2.0","id":2,"method":"tools/list","params":{}}\n' | node dist/index.js

{
  "mcpServers": {
    "weather": {
      "command": "node",
      "args": ["E:/AI_projects/weather-mcp-server/dist/index.js"]
    }
  }
}

## 触发条件
当用户询问天气、出行建议、气温相关信息时激活。

## 工作流程
1. 先用 geocode 将城市名转为坐标
2. 如果是"当前/现在就"，调用 get_current_weather
3. 如果是"明天/周末/下周"，调用 get_weather_forecast
4. 如果涉及多个城市对比，逐个查询后汇总
5. 用自然语言回答，突出关键信息

## 输出规范
- 默认用摄氏度
- 如果降雨概率 > 50%，提醒带伞
- 如果温度 > 30°C，提醒防暑
- 如果温度 < 10°C，提醒保暖