weather-mcp

MCP server wrapping Open-Meteo for an LLM voice assistant.

Overview

weather-mcp exposes weather lookup as a pair of MCP tools backed by the public Open-Meteo API. The intended consumer is an LLM-driven voice assistant: tool output is fed to the model as context, not always read aloud verbatim. Because of that, responses are short TTS-friendly prose and each weather response opens with the local time at the queried location, so the model can reason about freshness ("rain this afternoon" makes no sense at 11 PM).

Tools

Tool	Parameters	Returns
get_current_weather	location: str	One TTS-friendly sentence: current temperature, feels-like, sky conditions, wind.
get_forecast	location: str, days: int (1–14)	TTS-friendly paragraph, one sentence per day.

Disambiguation. A bare city like Paris returns a spoken list of options. Adding a qualifier — Paris, France or Paris, TX — picks one.

Day clamping. days values outside 1–14 are clamped, and the response opens with a brief acknowledgment of the clamp.

Requirements

• Python 3.13+
• uv for environment and dependency management
• Internet access (Open-Meteo public API; no API key required)

Install

uv sync

Run

uv run weather-mcp

By default the server binds 0.0.0.0:8001 and speaks the SSE transport. Override the bind with --host and --port, or with the environment variables WEATHER_MCP_HOST and WEATHER_MCP_PORT. CLI flags take precedence over environment variables.

Connecting a client

Any MCP client that supports the SSE transport can connect by pointing at http://<host>:8001/sse. Schemas vary by client; the snippet below shows where the URL goes:

{
  "mcpServers": {
    "weather": {
      "url": "http://<host>:8001/sse"
    }
  }
}

Development

uv run pytest

Tests use respx to stub Open-Meteo HTTP calls; no network is required.

Deployment (systemd)

Save as /etc/systemd/system/weather-mcp.service:

[Unit]
Description=Weather MCP server
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
WorkingDirectory=/opt/weather-mcp
ExecStart=/opt/weather-mcp/.venv/bin/weather-mcp
Restart=on-failure
RestartSec=5

[Install]
WantedBy=multi-user.target

Then:

systemctl daemon-reload
systemctl enable --now weather-mcp
journalctl -u weather-mcp -f

To bind a different address or port, set Environment=WEATHER_MCP_HOST=... and/or Environment=WEATHER_MCP_PORT=... in the unit's [Service] section.

Project layout

• main.py — FastMCP server, tool functions, lifespan, SSE entrypoint.
• open_meteo.py — HTTP I/O for Open-Meteo geocoding and forecast endpoints.
• formatting.py — TTS-friendly prose builders.

Changelog

See CHANGELOG.md.

License

Licensed under the Apache License 2.0; full text in LICENSE.