meteoswiss-mcp 0.3.3

MCP Server for Swiss weather and climate data — MeteoSwiss SwissMetNet, ICON forecasts, climate normals

🌦️ meteoswiss-mcp

MCP server for Swiss weather and climate data from MeteoSwiss.

Connects AI models to the SwissMetNet measurement network (160+ stations, 10-minute interval), MeteoSwiss ICON-CH1/CH2-EPS forecasts and climate normals 1991–2020. Part of the swiss-public-data-mcp portfolio.

🇩🇪 Deutsche Version

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Demo query (anchor example)

How suitable is next Wednesday for the sports day at Leutschenbach school?

→ meteo_school_check(location="Zürich Oerlikon", activity="Sporttag") returns a 🟢/🟡/🔴 traffic light for each day of the coming week — straight from the MeteoSwiss ICON model.

Combined with swiss-environment-mcp:

How were air quality and weather at Leutschenbach school yesterday?

→ meteo_current(station='REH') + env_nabel_current(station='ZUE') = a complete environmental picture. → More use cases by audience →

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Tools (6)

Tool	Description	Data source
meteo_stations	List SwissMetNet stations (filterable by canton)	Embedded
meteo_current	Current 10-min observations for a station	BGDI STAC API
meteo_forecast	1–16 day forecast for a place or coordinates	Open-Meteo / MeteoSwiss ICON
meteo_school_check	🟢/🟡/🔴 traffic light for outdoor school events	Open-Meteo / MeteoSwiss ICON
meteo_climate_normals	Monthly climate normals 1991–2020	Embedded (KLO, SMA, BER, LUG, GVE)
meteo_warnings	Current weather warnings & links	opendata.swiss + links

Tool annotations (MCP hints)

All tools carry explicit MCP annotations — relevant for the client approval UI and for the LLM's safety decisions.

Tool	readOnlyHint	destructiveHint	idempotentHint	openWorldHint
meteo_stations	✅	✗	✅	✗ (curated list)
meteo_current	✅	✗	✗ (live data)	✅ (upstream STAC)
meteo_forecast	✅	✗	✗ (live data)	✅ (upstream Open-Meteo)
meteo_school_check	✅	✗	✗ (live data)	✅ (geocoding + forecast)
meteo_climate_normals	✅	✗	✅	✗ (embedded normals)
meteo_warnings	✅	✗	✗ (live data)	✅ (opendata.swiss)

Read rules: all 6 tools are readOnly + non-destructive — the server fundamentally cannot write or delete anything. idempotentHint=False marks tools that return different values depending on when they are called.

MCP protocol version

Aspect	Value
Tested spec versions	2024-11-05, 2025-03-26, 2025-06-18 (via the mcp[cli] SDK)
FastMCP SDK version	see pyproject.toml → mcp[cli]>=1.0.0
Update policy	Dependabot watches mcp[cli]; spec bumps are documented in the CHANGELOG with a "Tool Definition Changes" marker

→ Full roadmap & update strategy: docs/roadmap.md

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Quick start

Claude Desktop

{
  "mcpServers": {
    "meteoswiss": {
      "command": "uvx",
      "args": ["meteoswiss-mcp"]
    }
  }
}

Claude Desktop (local development)

{
  "mcpServers": {
    "meteoswiss": {
      "command": "uv",
      "args": ["run", "--directory", "/path/to/meteoswiss-mcp", "meteoswiss-mcp"]
    }
  }
}

Cloud / Render.com (Streamable HTTP)

Configuration via ENV variables (the CLI flags --http / --port N still work as an override):

Variable	Default	Meaning
MCP_TRANSPORT	stdio	stdio or streamable-http
MCP_HOST	127.0.0.1	Bind address — never change locally
MCP_PORT	8000	Port
MCP_ALLOW_ANY_HOST	unset	Must be set to 1 to allow the server to bind to 0.0.0.0 (containers/cloud only)
MCP_LOG_LEVEL	INFO	DEBUG / INFO / WARNING / ERROR — structured JSON logs on stderr
MCP_ALLOWED_ORIGINS	unset	Comma-separated list of allowed origins for CORS. Empty = CORS disabled (same-origin only). Mcp-Session-Id is exposed automatically.
MCP_API_KEY	unset	If set: every request except /health requires X-API-Key: <key> or Authorization: Bearer <key>. Constant-time comparison.
MCP_STATELESS_HTTP	0	1 enables FastMCP stateless mode → each HTTP request opens a new session. Prerequisite for multi-replica deploys without sticky sessions (SCALE-002/003).
OTEL_EXPORTER_OTLP_ENDPOINT	unset	If set + pip install meteoswiss-mcp[otel]: OpenTelemetry spans per tool call + automatic httpx instrumentation are sent as OTLP-HTTP to the collector.
OTEL_SERVICE_NAME	meteoswiss_mcp	Service name in the OTel resources
MCP_CACHE_ENABLED	1	0 disables the TTL cache entirely (e.g. for end-to-end tests)
MCP_CACHE_TTL_STAC	300	TTL in seconds for STAC SMN observations (default 5 min)
MCP_CACHE_TTL_OPEN_METEO	600	TTL for ICON forecasts (default 10 min)
MCP_CACHE_TTL_GEOCODING	3600	TTL for geocoding lookups (default 1 h)
MCP_CACHE_TTL_OPENDATA	3600	TTL for the opendata.swiss catalogue (default 1 h)
MCP_CACHE_TTL_WARNINGS	300	TTL for the structured warnings API (default 5 min)
MCP_CLIMATE_NORMALS_PATH	unset	Path to a JSON file with additional climate normals — see data/climate-normals.example.json
MCP_WARNINGS_API_URL	unset	URL of a structured MeteoSwiss warnings API. The host must be on the egress allow-list. Schema-tolerant (GeoJSON features, a warnings array or items).
MCP_CLIMATE_NORMALS_URL_TEMPLATE	unset	URL template for runtime lookup of climate normals (for stations without embedded or JSON values). Tokens: {station} (lowercase), {STATION} (uppercase), {param} (MeteoSwiss code tre200m0/rre150m0/sre000m0). Example: https://data.geo.admin.ch/.../{station}/{param}.txt. The host must be on the egress allow-list.

# Local test (safe, loopback only)
MCP_TRANSPORT=streamable-http meteoswiss-mcp

# Container / Render
MCP_TRANSPORT=streamable-http MCP_HOST=0.0.0.0 MCP_ALLOW_ANY_HOST=1 meteoswiss-mcp

Docker / Render

The repo includes a production-ready multi-stage Dockerfile (non-root user, HEALTHCHECK) and a render.yaml blueprint:

# Build + test locally
docker build -t meteoswiss-mcp .
docker run --rm -p 8000:8000 meteoswiss-mcp
curl http://127.0.0.1:8000/health   # → {"status":"ok","service":"meteoswiss-mcp"}

On Render: "New → Blueprint" → select the repo. Defaults (plan starter, Frankfurt, single instance) are set in render.yaml.

Important: numInstances: 1 is set deliberately — sticky-session routing for multi-replica (audit SCALE-002/003) is not yet implemented.

Structured logging

All tool invocations, upstream failures and egress blocks are emitted as JSON events on stderr (stdio-transport safe). Example:

{"tool": "meteo_forecast", "days": 7, "has_coords": false, "event": "tool_invoked", "level": "info", "timestamp": "2026-05-20T07:00:00Z"}
{"tool": "meteo_forecast", "endpoint": "geocoding", "error_type": "HTTPStatusError", "event": "upstream_failed", "level": "warning", "timestamp": "..."}
{"url": "https://evil.example.com/", "method": "GET", "reason": "host not in allow-list", "event": "egress_blocked", "level": "warning", "timestamp": "..."}

HTTP-mode security

• MCP_HOST deliberately defaults to 127.0.0.1 so that --http on a dev laptop is not accidentally exposed to the local subnet (audit finding SEC-016).
• All outgoing HTTP calls (including redirect follows) are validated against an allow-list: data.geo.admin.ch, api.open-meteo.com, geocoding-api.open-meteo.com, opendata.swiss. Other hosts and IP literals (in particular 169.254.169.254, RFC1918) are rejected with EgressBlocked (SEC-004 / SEC-021).
• CORS: disabled by default (same-origin only). Browser clients (e.g. claude.ai web) need MCP_ALLOWED_ORIGINS=<csv> — the Mcp-Session-Id header is then automatically in Access-Control-Expose-Headers (SDK-004).
• API-key auth: disabled by default. In a production HTTP setup, always set MCP_API_KEY=<random> — requests without a valid X-API-Key or Authorization: Bearer … are rejected with 401 (SEC-009 / SEC-013). /health stays open for container health probes.

Example: production HTTP stack

# 32 bytes of randomness as the auth key
export MCP_API_KEY=$(python -c "import secrets; print(secrets.token_urlsafe(32))")

MCP_TRANSPORT=streamable-http \
MCP_HOST=0.0.0.0 \
MCP_ALLOW_ANY_HOST=1 \
MCP_ALLOWED_ORIGINS=https://app.example.com \
MCP_API_KEY="$MCP_API_KEY" \
meteoswiss-mcp

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Example queries

School planning

Which days next week are suitable for a sports day in Zürich?
→ meteo_school_check(location="Zürich", activity="Sporttag")

What will the weather be at Leutschenbach school on Friday?
→ meteo_forecast(location="Zürich Oerlikon", days=5)

Show me current readings from the nearest MeteoSwiss station to Zürich-Schwamendingen.
→ meteo_current(station="REH")

Climate comparison

How much rain normally falls in June in Zürich?
→ meteo_climate_normals(station="KLO")

Is Lugano really much sunnier than Zürich? Show me the annual values.
→ meteo_climate_normals(station="LUG") + meteo_climate_normals(station="SMA")

Infrastructure & environment

Are there currently any weather warnings for the canton of Zürich?
→ meteo_warnings(canton="ZH")

Show me a 10-day forecast for the Heerenschürli sports facility with hourly values.
→ meteo_forecast(location="Sportanlage Heerenschürli Zürich", days=10, hourly=True)

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Architecture

Claude Desktop / AI agent
        │
        │ MCP (stdio / Streamable HTTP)
        ▼
meteoswiss-mcp (FastMCP)
        │
        ├── meteo_stations ──────────────── [embedded: ~20 SMN stations]
        │
        ├── meteo_current ───────────────── BGDI STAC API
        │                                   data.geo.admin.ch/api/stac/v1
        │                                   Collection: ch.meteoschweiz.ogd-smn
        │
        ├── meteo_forecast ──────────────── Open-Meteo
        ├── meteo_school_check ──────────── api.open-meteo.com/v1/meteoswiss
        │                                   (MeteoSwiss ICON-CH1/CH2-EPS, 1–2 km)
        │
        ├── meteo_climate_normals ───────── [embedded: normals 1991–2020]
        │
        └── meteo_warnings ──────────────── opendata.swiss CKAN + links

Data sources

Source	URL	License
BGDI STAC API (MeteoSwiss OGD)	data.geo.admin.ch/api/stac/v1	CC BY 4.0
Open-Meteo (MeteoSwiss ICON)	api.open-meteo.com/v1/meteoswiss	CC BY 4.0
Open-Meteo Geocoding	geocoding-api.open-meteo.com	CC BY 4.0
opendata.swiss CKAN	opendata.swiss/api/3/action	CC BY 4.0

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Safety & limits

Aspect	Details
Access	Read-only (readOnlyHint: true on all tools) — the server cannot modify or delete any data
Personal data	No personal data — all sources are aggregated, publicly available open data
Rate limits	Built-in per-query caps: max 50 results per API call, 30 s timeout
Authentication	No API keys required — all data sources are publicly accessible
Licenses	All data under CC BY 4.0 (MeteoSwiss Open Government Data)
Terms of Service	Subject to the ToS of the respective data sources: MeteoSwiss OGD, Open-Meteo, opendata.swiss

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Known limitations

ID	Tool	Description
BUG-01	meteo_current	STAC asset structure can vary per station; fallback to a direct link is implemented
LIM-01	meteo_climate_normals	Only 5 stations embedded (KLO, SMA, BER, LUG, GVE); the rest via an opendata.swiss link
LIM-02	meteo_warnings	A direct warnings REST API is planned from Q2 2026 (MeteoSwiss OGD phase 2); currently links + CAP
LIM-03	meteo_current	Shows 10-min values in UTC; no automatic conversion to local time

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Portfolio synergies

meteoswiss-mcp
    │
    ├── swiss-environment-mcp   Combine weather + air quality (NABEL)
    │                           "How were weather AND air at Leutschenbach school?"
    │
    └── zurich-opendata-mcp     School locations → weather forecast
                                "Which schools in Zürich have sports-day weather?"

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Testing

# Unit tests (no network)
PYTHONPATH=src pytest tests/ -m "not live" -v

# Live tests (real APIs)
PYTHONPATH=src pytest tests/ -m live -v

# Linting
ruff check src/ tests/

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Development

git clone https://github.com/malkreide/meteoswiss-mcp
cd meteoswiss-mcp
pip install -e ".[dev]"

MCP Inspector (local test)

PYTHONPATH=src npx @modelcontextprotocol/inspector python -m meteoswiss_mcp.server

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Contributing & Security

• Contributing guidelines (Deutsch)
• Security policy (Deutsch)

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License

MIT License – see LICENSE.

Source data: MeteoSwiss Open Government Data (CC BY 4.0). When using the data, cite: Source: MeteoSwiss.

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