# faregrid

faregrid is a small local bridge to the hosted
FlightPowers MCP server, which reads live flight prices
from Google Flights. Give it an origin and a destination,
plus either a single date or a whole date range, and it
answers with fares, airlines, durations, stop counts, a
bookable link for each flight, and the historical price
band that shows whether a fare is unusually cheap or
expensive for that route.

The bridge keeps no fare data of its own. It serves the
upstream server's tool list locally, exactly as captured
from the live endpoint, and forwards each tool call
upstream, returning the result untouched. The captured
surface is search only: results carry a `buy_link` to
book on the vendor's own flow, and there is no booking,
purchase, or payment tool in it.

## Tools

- `search_oneway_flights` — one-way fares. Required:
  `from_airport` and `to_airport` (IATA codes; the
  destination may be several codes as `"BCN,LIS,ATH"` or
  `["BCN","LIS","ATH"]`). Optional: `departure_date`, or
  a range via `departure_date_from` / `departure_date_to`,
  `max_stops`, `airline_codes`, `exclude_airline_codes`,
  departure and arrival hour windows, `currency`
  (default `"usd"`), `max_price`, `seat_type`,
  `passengers`, `sort_by` (default `"best"`), `limit`
  (default 10), `max_searches`, `use_fallback`, and
  `verbose`. One call can search every date/destination
  combination in a range.
- `search_roundtrip_flights` — round-trip fares, priced
  as paired legs rather than two separate one-ways.
  Required: `from_airport` and `to_airport`. Optional:
  the same departure date or range fields as the one-way
  tool, plus `return_date` or `nights` (a trip length, or
  a list like `[5, 6, 7]`), `max_departure_stops`,
  `max_return_stops`, `departure_airline_codes`,
  `return_airline_codes`, `returns_per_outbound`, and
  the shared `currency`, `max_price`, `seat_type`,
  `passengers`, `sort_by`, `limit`, `max_searches`,
  `use_fallback`, and `verbose` fields.

Fares go stale within minutes, so a current price always
comes from a new search rather than an earlier result.

## Configuration

- `FLIGHTPOWERS_MCP_URL` (optional) — override the
  upstream endpoint. Defaults to
  `https://flights.flightpowers.com/mcp`. (The override
  hook is this rebuild's own labelled reconstruction.)
- `FLIGHTPOWERS_API_KEY` (optional) — when set, every
  upstream request carries an
  `x-rapidapi-key: <key>` header, for the caller's own
  RapidAPI key for the Google Flights Live API. When it
  is not set, no key header is sent and the upstream
  applies its free sign-in allowance. No `Authorization`
  header is ever sent. (This forwarding is also a
  labelled reconstruction; the original surface was
  captured keyless.)

### Forwarding mechanics

On the first tool call the client opens a streamable
HTTP session with the upstream: a JSON-RPC `initialize`
request (protocolVersion `2025-03-26`, clientInfo name
`faregrid`), then a `notifications/initialized`
notification, then the `tools/call` request carrying
the caller's arguments unchanged. When the upstream
answers `initialize` with an `Mcp-Session-Id` header,
that value rides on every later request of the session,
which is reused for the life of the process. Replies
may arrive as plain JSON or as server-sent events;
both are read.

Successful upstream results pass through verbatim,
including any `isError` flag the upstream sets.
Failures — a JSON-RPC error, a non-2xx status, an
unreadable response, or a request that cannot be
completed — come back as an `isError` result whose
text starts with `faregrid error:` (this rendering
is this rebuild's own labelled reconstruction).

## CLI

Each tool is also a subcommand taking one JSON argument
string:

```bash
npx @reneturcios/faregrid search_oneway_flights '{"from_airport":"TLV","to_airport":"BCN","departure_date":"2026-11-10"}'
npx @reneturcios/faregrid search_roundtrip_flights '{"from_airport":"TLV","to_airport":"BCN,LIS","departure_date_from":"2026-11-01","departure_date_to":"2026-11-07","nights":[3,4]}'
npx @reneturcios/faregrid --version
```

Exit codes: `0` on success, `1` on an `isError`
result, `2` on a usage error.

## MCP server

```bash
npx -y @reneturcios/faregrid mcp
```

MCP client config:

```json
{
  "mcpServers": {
    "faregrid": {
      "command": "npx",
      "args": ["-y", "@reneturcios/faregrid", "mcp"]
    }
  }
}
```

## Docker

```bash
docker run -i ghcr.io/cloudcorprecords/faregrid
docker run --rm ghcr.io/cloudcorprecords/faregrid --version
```

The container's default command is `mcp`, so the first
form is a stdio MCP server; any other arguments reach
the CLI normally.

## Development

```bash
npm install
npm run build
npm test
npm run dev
```

The test suite runs entirely against a stubbed
JSON-RPC upstream — no live network calls.

## License

MIT — see `LICENSE`.