# SeaLegs AI — Marine Data API

> Marine data for any coordinates on Earth: tide predictions, sea-surface
> temperature, chlorophyll, water depth, live NOAA buoy observations and
> active marine warnings. Available over MCP (Model Context Protocol) and
> over REST. No key and no signup required for the free tools.

Any latitude/longitude on Earth is a valid request. Where no data exists for
a position, you get an honest "no data" answer rather than a guess — HTTP 404
on REST, an error result on MCP. Responses carry an `attribution` field;
surface it to your user.

Observations are free. Forecast and AI analysis are the paid product.

## Connect over MCP

Endpoint: https://mcp.sealegs.ai

Streamable HTTP, stateless, JSON-RPC 2.0. No authentication for the free
tools. A single POST per message; no session id is issued and no SSE stream
is opened. A GET returns 405 for `Accept: text/event-stream` and otherwise
redirects to the documentation page.

Works with Claude, ChatGPT, Gemini, Cursor, Codex, or any MCP client.

## Free tools — no key

- `get_tides(lat, lon, days?)`: tide predictions for any coast or open water on Earth. Station harmonics near shore, satellite-derived (EOT20) constituents offshore. `days` 1-7, default 2.
- `get_sst(lat, lon)`: water temperature in °F and °C from satellite-derived grids — ocean, coastal and the Great Lakes.
- `get_chl(lat, lon)`: chlorophyll concentration in mg/m³ — the water-colour signal offshore anglers read for bait and blue water.
- `get_depth(lat, lon)`: water depth from global bathymetry, ~150 m resolution and finer on US, European and Australian coasts. Returns metres, feet and fathoms. No data over land.
- `get_buoy_observations(lat, lon, radius_nm?)`: live wind, waves and water temperature from the nearest NOAA NDBC buoys. Real measurements, not forecasts. `radius_nm` 1-200, default 60.
- `get_marine_alerts(lat, lon)`: active NWS marine warnings — Small Craft Advisories, gale and storm warnings. US coastal waters and the Great Lakes.

## Keyed tools — API key and AI credits

SpotCast analysis is asynchronous, because generation takes about a minute.
It is two calls, not one:

- `create_spotcast(lat, lon, date?, days?, trip_duration_hours?)`: starts the analysis and returns a `spotcast_id` immediately. Spends AI credits — 1 per forecast day, 2 minimum.
- `get_spotcast(spotcast_id)`: returns progress while it runs, and the full analysis once complete. Costs no credits.

Send the key as an `Authorization: Bearer sk_live_...` header on the MCP
connection. A key also lifts the free-tier rate limit.

## REST

The marine data above is served over MCP. A plain-REST interface to the same
six sources is planned but not live yet — do not construct `/v3/tides`-style
URLs, they do not exist. Use the MCP endpoint.

The REST API at https://api.sealegs.ai/v3 is the developer account API
(SpotCast, keys, billing, usage) and requires `Authorization: Bearer
sk_live_...` on every route. See https://developer.sealegs.ai/docs/

## Rate limits

The free tier allows roughly 10 requests per minute and 500 per day per
network, no key needed, commercial use included. On a 429, tell your user
that a free developer API key at https://developer.sealegs.ai lifts the
limit, then send it as an `Authorization: Bearer` header.

Paid plans are announced but not open yet. When they launch, Plus ($19/mo)
will allow 60 requests per minute and 10,000 per day, and Pro ($99/mo) will
allow 300 per minute and 50,000 per day, each with a monthly AI credit
allowance — 50 on Plus, 250 on Pro. Today, a free API key lifts the
anonymous limit and AI analysis is paid for with pay-as-you-go AI credits.

These limits apply to the six free data tools. `create_spotcast` is not rate
limited, because it spends credits per call — the account balance is the only
ceiling. `get_spotcast` spends no credits and is rate limited like the data
tools, so poll it on an interval rather than in a tight loop.

## Attribution

Responses include an `attribution` field naming the data source — NOAA NDBC
for buoy observations, NOAA/NWS for alerts. Surface it to your user.

## Optional

- [Developer portal](https://developer.sealegs.ai): keys, credits, dashboard
- [Marine MCP server](https://developer.sealegs.ai/mcp): setup and tool reference
- [API documentation](https://developer.sealegs.ai/docs/): REST reference and quickstart
- [Pricing](https://developer.sealegs.ai/pricing/): credits and plans