# HALOWERK Eastern Land – HR Max Slope

> HALOWERK Eastern Land – HR Max Slope is a paid API for AI agents from ostland.halowerk.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-15).

Returns the maximum adjacent-cell surface gradient (steepest slope) across the analysis grid for a given coordinate within Croatia.

## Facts

- Endpoint: POST https://ostland.halowerk.com/v1/hr-max-slope
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/halowerk-eastern-land-hr-max-slope-c49fb64c
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ovUqYF4h5Pp2nRsETKxYU

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 halowerk-eastern-land-hr-max-slope-c49fb64c -d '<json body>'
```

Example prompt: What's the maximum surface slope gradient at latitude 45.32, longitude 16.45 in Croatia? I need the steepest adjacent-cell terrain gradient for that point.

## When to prefer this

Choose this endpoint when you need the steepest terrain slope metric for a specific point within Croatia and want boundary validation guaranteed before billing. It is purpose-built for Croatian land analysis with built-in coordinate rejection outside the national boundary, making it reliable for agricultural suitability, construction planning, or erosion risk workflows in Croatia specifically. Prefer alternatives if you need slope data outside Croatia or require mean/median slope rather than the maximum adjacent-cell gradient.

## Known failure modes

- Coordinate outside Croatia's Natural Earth boundary — request rejected before payment, returns validation error
- Latitude or longitude outside the published European coverage range (lat 34–72.5, lon -31.5–40.5) — schema validation error
- Malformed or missing coordinate fields — returns input validation error
- Network or service timeout — no result returned
- Ambiguous or borderline boundary coordinates may be rejected conservatively

## How this service works

Maximum adjacent-cell surface gradient across the analysis grid. The coordinate is validated against the Natural Earth boundary for Croatia; results outside it are rejected before payment.

## Output

A numeric value representing the maximum adjacent-cell surface gradient (steepest slope angle or ratio) computed across the analysis grid centered on the submitted coordinate. Coordinates outside Croatia's boundary are rejected before any computation or payment is processed.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "latitude": {
   "type": "number",
   "maximum": 72.5,
   "minimum": 34,
   "description": "WGS84 latitude inside the published European coverage."
  },
  "longitude": {
   "type": "number",
   "maximum": 40.5,
   "minimum": -31.5,
   "description": "WGS84 longitude inside the published European coverage."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/halowerk-eastern-land-hr-max-slope-c49fb64c/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from ostland.halowerk.com](https://www.zero.xyz/host/ostland.halowerk.com/llms.txt)