# Karte Halowerk Tide Predictions

> Karte Halowerk Tide Predictions is a paid API for AI agents from karte.halowerk.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).

Returns NOAA CO-OPS tide predictions (high/low water times and heights) for a station over a time window, plus observed water level and residual deviation from astronomical forecast where available.

## Facts

- Endpoint: POST https://karte.halowerk.com/v1/tides
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/karte-halowerk-tide-predictions-cfe5718b
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_sI4XZmjP2w6q45Q8YWPOt

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability karte-halowerk-tide-predictions-cfe5718b -d '<json body>'
```

Example prompt: What are the high and low tides at NOAA station 8443970 (Boston) from now through this Saturday, and how far is the current observed water level from the astronomical prediction?

## When to prefer this

Choose this endpoint when you need precise tidal extremes (times and heights of highs and lows) from an official NOAA CO-OPS gauge, especially when the residual between observed and predicted water level matters — for example near navigational depth limits, flood thresholds, or any situation where wind and pressure effects on water level are operationally significant. Prefer this over generic tide APIs when NOAA station-level accuracy and real-time observed level comparison are required.

## Known failure modes

- Invalid or unknown NOAA station ID — station not found error
- Time window too large or outside available data range
- NOAA CO-OPS upstream service unavailable — upstream fetch error
- Station lacks real-time sensors — observed level and residual not returned
- Malformed request body — missing required fields like station ID or time window

## How this service works

Returns tide predictions for a NOAA CO-OPS station: every high and low water in the window with its time and height above datum, the range between them, and which extreme comes next with the time remaining. Where the station also measures, the observed water level is fetched and compared with the prediction — wind and air pressure routinely push the real level away from the astronomical forecast, and that residual is the figure that matters for anyone near a limit, so it is returned rather than…

## Output

A list of all high and low water events in the requested window, each with timestamp, height above datum, and tidal range. Includes which extreme event comes next and the time remaining until it. Where the station has live sensors, returns the current observed water level alongside the astronomical prediction and the residual difference (actual minus predicted), which captures meteorological forcing such as wind setup and barometric pressure effects.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "days": {
   "type": "integer",
   "default": 2,
   "maximum": 7,
   "minimum": 1,
   "description": "How many days of predictions."
  },
  "datum": {
   "enum": [
    "MLLW",
    "MSL",
    "MHW",
    "NAVD"
   ],
   "type": "string",
   "default": "MLLW",
   "description": "Vertical datum heights are given against."
  },
  "units": {
   "enum": [
    "metric",
    "english"
   ],
   "type": "string",
   "default": "metric",
   "description": "metric = metres, english = feet."
  },
  "station": {
   "type": "string",
   "maxLength": 20,
   "description": "NOAA station id, e.g. 8454000. Either this or a coordinate."
  },
  "latitude": {
   "type": "number",
   "maximum": 90,
   "minimum": -90,
   "description": "Latitude; the nearest station is used."
  },
  "longitude": {
   "type": "number",
   "maximum": 180,
   "minimum": -180,
   "description": "Longitude."
  },
  "include_observed": {
   "type": "boolean",
   "default": true,
   "description": "Also fetch the measured level and compare it with the prediction."
  },
  "max_station_distance_km": {
   "type": "number",
   "default": 100,
   "maximum": 500,
   "minimum": 1,
   "description": "Refuse a coordinate whose nearest station is further away than this."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/karte-halowerk-tide-predictions-cfe5718b/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from karte.halowerk.com](https://www.zero.xyz/host/karte.halowerk.com/llms.txt)