aviation-weather-mcp-server

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  <h1>@cyanheads/aviation-weather-mcp-server</h1>
  <p><b>Fetch METARs, TAFs, PIREPs, and domestic SIGMETs from the NWS Aviation Weather Center via MCP. STDIO or Streamable HTTP.</b>
  <div>5 Tools • 1 Prompt</div>
  </p>
</div>

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**Public Hosted Server:** [https://aviation-weather.caseyjhand.com/mcp](https://aviation-weather.caseyjhand.com/mcp)

</div>

---

## Tools

Five tools covering aviation weather — station lookup, current observations, terminal forecasts, pilot reports, and active advisories:

| Tool | Description |
|:-----|:------------|
| `aviation_find_stations` | Resolve airports and weather stations by ICAO ID, bounding box, or US state. Returns ICAO/IATA/FAA IDs, coordinates, elevation, and available data types. |
| `aviation_get_metar` | Get current weather observations (METARs) for one or more airports. Returns decoded wind, visibility, ceiling, present weather, temp/dewpoint, altimeter, cloud layers, flight category (VFR/MVFR/IFR/LIFR), and the raw METAR string. |
| `aviation_get_taf` | Get Terminal Aerodrome Forecasts for one or more airports. Returns each forecast period with valid times, surface wind, low-level wind shear, visibility, decoded weather, cloud layers, and vertical visibility into a forecast obscuration, plus the raw TAF string. |
| `aviation_get_pireps` | Get recent Pilot Reports near an airport or within a bounding box. Returns decoded turbulence, icing, and cloud reports with altitude, aircraft type, intensity, and the raw PIREP string. |
| `aviation_get_advisories` | Get active domestic SIGMETs for a region. Returns hazard type (CONVECTIVE, TURBULENCE, ICING, IFR), severity, altitude range, valid period, polygon coordinates, and raw text. |

### `aviation_find_stations`

Resolve and discover weather stations by multiple search modes.

- Look up one or more stations by 4-letter ICAO ID (up to 20 IDs per call) — lookup is ICAO-only, but each returned record includes its IATA/FAA aliases when available
- Discover all stations within a geographic bounding box
- List stations for one of the 50 US states or DC via two-letter USPS code (uses bbox + client-side state filter)
- Returns `data_types` (METAR, TAF, etc.) so agents can confirm what's available before querying
- Every result states whether the upstream 400-row cap cut it, so a truncated draw is never mistaken for every station in the area — a capped state query also reports the row count from before the state filter, and a smaller `bbox` is the named lever

---

### `aviation_get_metar`

Fetch current or recent METAR observations (1–10 stations per call).

- `hours` parameter (1–12) returns observation history per station; default 1 returns only the most recent
- Flight category (VFR/MVFR/IFR/LIFR) is returned directly from the AWC API — no client-side computation needed
- Decodes cloud layers, wind with gusts, visibility, and present weather (the raw groups plus plain English, one reading per group) in addition to the raw METAR string
- Ceiling covers broken, overcast, and obscuration layers, and reports whether the height was measured or is an indefinite ceiling — vertical visibility into an obscuration
- METAR type field distinguishes `METAR` (routine) from `SPECI` (special observation triggered by significant weather change)
- Every batch reports which of the requested stations came back, so a partial result is never mistaken for full coverage — missing IDs are named with recovery guidance

---

### `aviation_get_taf`

Fetch Terminal Aerodrome Forecasts for 1–4 airports.

- Returns structured forecast periods with change types (`FM`, `TEMPO`, `BECMG`) and probabilities
- Forecast weather decoded group by group beside the raw groups (`-SHRA BR` → `light rain showers; mist`), the same shape `aviation_get_metar` returns
- Forecast obscurations keep their layer and carry the vertical visibility into them (`VV002` → a 200 ft indefinite ceiling), rather than reading as a clear sky
- Low-level wind shear (`WS020/20040KT`) is decoded to the shear-layer top and the forecast wind at that height
- `valid_from` / `valid_to` in ISO 8601 for straightforward time comparisons
- Every batch reports which of the requested stations came back, so a partial result is never mistaken for full coverage — missing IDs are named with recovery guidance

---

### `aviation_get_pireps`

Search for recent Pilot Reports by station+radius or bounding box.

- `station_id` + `distance_nm` (10–500 nm, 100 when omitted) for radial search around an airport
- `bbox` for geographic area search — useful for en-route corridor checks; `distance_nm` has no meaning here and is rejected alongside it
- `altitude_min_ft` / `altitude_max_ft` filters to isolate reports at cruise altitude, either bound alone or both (min must not exceed max)
- Turbulence and icing arrays include up to two layers per report (as reported by the API)
- Every result states whether the upstream 400-row cap cut it, naming `bbox`, `distance_nm`, and `hours` as the levers that narrow a query before the cap applies — the altitude filter runs after it and cannot recover a dropped report
- Note: absence of PIREPs does not mean smooth conditions — they are sparse by nature

---

### `aviation_get_advisories`

List currently active domestic SIGMETs.

- `advisory_type` filter: `sigmet` or `all` (default) — both return the active SIGMET set
- `hazard` filter: `CONVECTIVE`, `TURBULENCE`, `ICING`, `IFR`
- `bbox` filter applied client-side (AWC API returns all active advisories; the tool filters by polygon overlap)
- AIRMETs are not served. The upstream feed carries domestic SIGMETs only, so `advisory_type: airmet` and the `MTN OBSCN`, `SURFACE WIND`, and `LLWS` hazards are rejected with guidance rather than answered with SIGMETs or an empty array
- During fair-weather periods, no SIGMETs may be active — an empty result is a valid state, not an error

---

## Prompts

| Type | Name | Description |
|:-----|:-----|:------------|
| Prompt | `aviation_preflight_brief` | Structure a preflight weather briefing for one or more airports. Guides the LLM to call `aviation_get_metar`, `aviation_get_taf`, and `aviation_get_advisories` in sequence and synthesize a go/no-go picture with flight categories and active hazards. |

All resource data is reachable via tools. This server has no resources — all aviation weather data is time-sensitive (METARs valid ~1 hour, advisories minutes to hours) and unsuitable for stable-URI resources.

---

## Features

Built on [`@cyanheads/mcp-ts-core`](https://www.npmjs.com/package/@cyanheads/mcp-ts-core):

- Declarative tool and prompt definitions — single file per primitive, framework handles registration and validation
- Unified error handling — handlers throw, framework catches, classifies, and formats
- Pluggable auth: `none`, `jwt`, `oauth`
- Structured logging with optional OpenTelemetry tracing
- STDIO and Streamable HTTP transports

Aviation-weather-specific:

- Keyless — no API key or authentication required; all data is from the public AWC Data API
- Single service (`aviation-weather-service`) with retry + exponential backoff for the keyless public endpoint
- Raw coded strings (`rawOb`, `rawTAF`, `rawAirSigmet`) surfaced alongside decoded fields so agents have both layers
- State→bbox table enables US-state station queries that the AWC API doesn't natively support
- Server-level `instructions` field surfaces the "not an official briefing" safety disclaimer to all clients on `initialize`

Agent-friendly output:

- Flight category (`VFR`/`MVFR`/`IFR`/`LIFR`) as a discriminated string field — agents can branch on it without parsing ceiling + visibility
- Structured error contracts with typed `reason` fields and `recovery` hints (e.g., "Verify ICAO IDs with `aviation_find_stations`")
- `aviation_preflight_brief` prompt encodes the correct METAR → TAF → PIREPs → advisories briefing sequence that agents frequently get wrong by omitting steps

-