MCP笔记01: 快速创建一个MCP Server

1uv init -p 3.12 weather
2
3cd weather

1uv venv
2source .venv/bin/activate

1uv add "mcp[cli]" httpx

 1from typing import Any
 2import httpx
 3from mcp.server.fastmcp import FastMCP
 4
 5
 6mcp = FastMCP("weather")
 7
 8# Constants
 9NWS_API_BASE = "https://api.weather.gov"
10USER_AGENT = "weather-app/1.0"

 1async def make_nws_request(url: str) -> dict[str, Any] | None:
 2    """Make a request to the NWS API with proper error handling."""
 3    headers = {"User-Agent": USER_AGENT, "Accept": "application/geo+json"}
 4    async with httpx.AsyncClient() as client:
 5        try:
 6            response = await client.get(url, headers=headers, timeout=30.0)
 7            response.raise_for_status()
 8            return response.json()
 9        except Exception:
10            return None
11
12
13def format_alert(feature: dict) -> str:
14    """Format an alert feature into a readable string."""
15    props = feature["properties"]
16    return f"""
17Event: {props.get('event', 'Unknown')}
18Area: {props.get('areaDesc', 'Unknown')}
19Severity: {props.get('severity', 'Unknown')}
20Description: {props.get('description', 'No description available')}
21Instructions: {props.get('instruction', 'No specific instructions provided')}
22"""

 1@mcp.tool()
 2async def get_alerts(state: str) -> str:
 3    """Get weather alerts for a US state.
 4
 5    Args:
 6        state: Two-letter US state code (e.g. CA, NY)
 7    """
 8    url = f"{NWS_API_BASE}/alerts/active/area/{state}"
 9    data = await make_nws_request(url)
10
11    if not data or "features" not in data:
12        return "Unable to fetch alerts or no alerts found."
13
14    if not data["features"]:
15        return "No active alerts for this state."
16
17    alerts = [format_alert(feature) for feature in data["features"]]
18    return "\n---\n".join(alerts)
19
20
21@mcp.tool()
22async def get_forecast(latitude: float, longitude: float) -> str:
23    """Get weather forecast for a location.
24
25    Args:
26        latitude: Latitude of the location
27        longitude: Longitude of the location
28    """
29    # First get the forecast grid endpoint
30    points_url = f"{NWS_API_BASE}/points/{latitude},{longitude}"
31    points_data = await make_nws_request(points_url)
32
33    if not points_data:
34        return "Unable to fetch forecast data for this location."
35
36    # Get the forecast URL from the points response
37    forecast_url = points_data["properties"]["forecast"]
38    forecast_data = await make_nws_request(forecast_url)
39
40    if not forecast_data:
41        return "Unable to fetch detailed forecast."
42
43    # Format the periods into a readable forecast
44    periods = forecast_data["properties"]["periods"]
45    forecasts = []
46    for period in periods[:5]:  # Only show next 5 periods
47        forecast = f"""
48{period['name']}:
49Temperature: {period['temperature']}°{period['temperatureUnit']}
50Wind: {period['windSpeed']} {period['windDirection']}
51Forecast: {period['detailedForecast']}
52"""
53        forecasts.append(forecast)
54
55    return "\n---\n".join(forecasts)

1if __name__ == "__main__":
2    # Initialize and run the server
3    mcp.run(transport="stdio")

 1{
 2  "mcpServers": {
 3    "aPS_XksxKP-paDOrI1zqP": {
 4      "name": "weather",
 5      "type": "stdio",
 6      "description": "",
 7      "isActive": true,
 8      "registryUrl": "",
 9      "command": "uv",
10      "args": [
11        "--directory",
12        "/ABSOLUTE/PATH/TO/PARENT/FOLDER/weather",
13        "run",
14        "weather.py"
15      ]
16    }
17  }
18}