构建你的第一个 MCP Server

uv init weather
cd weather
uv venv
source .venv/bin/activate
uv add "mcp[cli]"
touch weather.py

from typing import Any
from mcp.server import MCPServer
import httpx2

mcp = MCPServer("weather")
NWS_API_BASE = "https://api.weather.gov"
USER_AGENT = "weather-app/1.0"

async def make_nws_request(url: str) -> dict[str, Any] | None:
    headers = {"User-Agent": USER_AGENT, "Accept": "application/geo+json"}
    async with httpx2.AsyncClient() as client:
        try:
            response = await client.get(url, headers=headers, timeout=30.0)
            response.raise_for_status()
            return response.json()
        except Exception:
            return None

def format_alert(feature: dict) -> str:
    props = feature["properties"]
    return (
        f"Event: {props.get('event', 'Unknown')}\n"
        f"Area: {props.get('areaDesc', 'Unknown')}\n"
        f"Severity: {props.get('severity', 'Unknown')}\n"
        f"Description: {props.get('description', 'No description available')}"
    )

@mcp.tool()
async def get_alerts(state: str) -> str:
    """Get weather alerts for a US state.

    Args:
        state: Two-letter US state code (e.g. CA, NY)
    """
    url = f"{NWS_API_BASE}/alerts/active/area/{state}"
    data = await make_nws_request(url)
    if not data or "features" not in data:
        return "Unable to fetch alerts or no alerts found."
    if not data["features"]:
        return "No active alerts for this state."
    return "\n---\n".join(format_alert(f) for f in data["features"])

@mcp.tool()
async def get_forecast(latitude: float, longitude: float) -> str:
    """Get weather forecast for a location."""
    points = await make_nws_request(f"{NWS_API_BASE}/points/{latitude},{longitude}")
    if not points:
        return "Unable to fetch forecast data for this location."
    forecast = await make_nws_request(points["properties"]["forecast"])
    if not forecast:
        return "Unable to fetch detailed forecast."
    periods = forecast["properties"]["periods"][:5]
    return "\n---\n".join(
        f"{p['name']}: {p['temperature']}{p['temperatureUnit']} / {p['detailedForecast']}"
        for p in periods
    )

if __name__ == "__main__":
    mcp.run(transport="stdio")

# 启动：
# uv run weather.py

{
  "mcpServers": {
    "weather": {
      "command": "uv",
      "args": [
        "--directory",
        "/ABSOLUTE/PATH/TO/PARENT/FOLDER/weather",
        "run",
        "weather.py"
      ]
    }
  }
}