# HALOWERK Eastern Land – Bulgaria Maximum Surface Slope

> HALOWERK Eastern Land – Bulgaria Maximum Surface 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 Bulgaria.

## Facts

- Endpoint: POST https://ostland.halowerk.com/v1/bg-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-bulgaria-maximum-surface-slope-80d35dc4
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_4UTr9ulc4xNFw4AEIlA87

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-bulgaria-maximum-surface-slope-80d35dc4 -d '<json body>'
```

Example prompt: What's the maximum adjacent-cell surface slope at latitude 42.15, longitude 24.75 in Bulgaria — I need the steepest terrain gradient for that location.

## When to prefer this

Use this endpoint when you need the single steepest slope metric (maximum adjacent-cell gradient) for a specific point within Bulgaria, particularly for terrain suitability analysis, construction screening, agricultural planning, or erosion risk assessment. Prefer it over generic elevation or DEM APIs when you specifically need maximum slope within Bulgaria and want built-in boundary validation.

## Known failure modes

- Coordinate outside Bulgaria boundary — rejected before processing or payment
- Latitude or longitude out of European coverage range (lat 34–72.5, lon -31.5–40.5) — validation error
- Malformed JSON input — request error
- Payment failure — transaction not completed, no result returned
- Service unavailable — upstream elevation data unreachable

## How this service works

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

## Output

A numeric value representing the maximum adjacent-cell surface gradient (steepest slope) across the analysis grid centered on the requested Bulgarian coordinate. Returns an error if the coordinate falls outside the validated Natural Earth boundary for Bulgaria.

## 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-bulgaria-maximum-surface-slope-80d35dc4/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)