emy-mcp

An MCP server for Greek weather data from EMY — the Hellenic National Meteorological Service (Εθνική Μετεωρολογική Υπηρεσία).

It wraps EMY's public (api.emy.gr) endpoints as MCP tools. No API key is required, and nothing is hardcoded — locations and data are always fetched live from EMY.

Tools

Related MCP server: IPMA MCP Server

Resolving a location

This is the tricky part. EMY stores names transliterated from Greek with a prefecture suffix, e.g. KORINTHOS (M. KORINTHIAS). Three independent problems:

1. Exonyms vs transliteration — "Corinth" ≠ "Korinthos", "Corfu" ≠ "Kerkyra".

2. Prefecture suffix on every name — (m. Korinthias).

3. Greek script + accents — Κόρινθος vs KORINTHOS.

How they're handled:

• Greek or Latin name → get_forecast(location=...) or list_locations(query=...). Names are accent-folded, suffix-stripped, and Greek is transliterated to Latin using EMY's own scheme, so Κόρινθος, korinthos and KORINTHOS all match. Fuzzy ranking handles typos and returns alternatives.

• English exonyms / anything ambiguous → resolve the place to coordinates and call get_forecast(latitude=..., longitude=...). This returns the nearest forecast point regardless of spelling or language (e.g. Corinth's coordinates → Korinthos, 5 km away). An LLM client typically knows the coordinates already.

Live data, caching & resilience

Everything is fetched live. Per endpoint:

1. Fresh window — cached payload is served without refetch for 30 minutes (EMY's forecasts update ~twice daily).

2. After the window, a refetch is attempted.

3. If EMY is unreachable, the last-known-good copy is served for up to 24 hours, flagged stale with its age.

4. After 24 hours with no successful fetch, the call fails with a clear error.

Every tool response includes a source block with fetched_at, age_minutes and stale.

TLS note

api.emy.gr serves a valid *.emy.gr certificate but omits the intermediate CA from the handshake, so standard clients fail with "unable to get local issuer certificate". The client fetches the intermediate (RapidSSL TLS RSA CA G1) from the certificate's own AIA URL on first use and caches it under ~/.cache/emy-mcp/. Because a fetched cert is installed as a trusted anchor, it is pinned by SHA-256 fingerprint — a fetched or cached cert is only trusted if its fingerprint matches the known-good value, which makes the fetch safe against tampering and self-heals a corrupt cache. Certificate verification is not disabled; if EMY ever rotates this CA the pin must be updated.

Data caveats

• Sky condition comes from a small icon set (6 values): Sunny, Hot, Partly cloudy, Scattered showers, Cloudy with rain, Thunderstorms — so it's coarse.

• Wind speed units are reported by EMY as a bare number; they appear to be m/s and are labelled as such, but EMY does not document this.

• There is no live "current observations" feed in EMY's public API — only forecasts, alerts, marine and climate. This server reflects that.

Install & run

pip install -e .          # or: pip install httpx certifi "mcp>=1.2"

# stdio (Claude Desktop, Claude Code, local assistants)
python -m emy_mcp

# streamable-HTTP (hostable)
python -m emy_mcp --http --host 0.0.0.0 --port 8000

Claude Desktop / Claude Code config (stdio)

{
  "mcpServers": {
    "emy-weather": {
      "command": "python",
      "args": ["-m", "emy_mcp"]
    }
  }
}

License

MIT