# HALOWERK Eastern Land – Hungary Mean First-Order Surface Slope

> HALOWERK Eastern Land – Hungary Mean First-Order 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 2026-09-13).

Returns the mean first-order surface gradient (slope) across the analysis grid for a given WGS84 coordinate validated to fall within Hungary's boundaries.

## Facts

- Endpoint: POST https://ostland.halowerk.com/v1/hu-mean-slope
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/halowerk-eastern-land-hungary-mean-first-order-surface-slope-2e3a4618
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_nBGFnGHqOk_57AgZxsGKW

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-hungary-mean-first-order-surface-slope-2e3a4618 -d '<json body>'
```

Example prompt: What's the mean surface slope at latitude 47.5 and longitude 19.05 in Hungary? I need the first-order gradient value for that location.

## When to prefer this

Use this endpoint when you need the mean first-order surface gradient specifically for a location within Hungary, and need boundary validation guarantees before incurring payment. Prefer this over generic elevation APIs when you specifically need slope (gradient) rather than raw elevation, and when Hungary-specific coverage and Natural Earth boundary enforcement is required.

## Known failure modes

- Coordinate outside Hungary boundary: request rejected before payment, returns boundary validation error
- Coordinate outside European coverage bounds (lat 34–72.5, lon -31.5–40.5): rejected with schema validation error
- Missing or malformed latitude/longitude: returns input validation error
- Payment failure via x402 protocol: request not processed

## How this service works

Mean first-order surface gradient across the analysis grid. The coordinate is validated against the Natural Earth boundary for Hungary; results outside it are rejected before payment.

## Output

A numeric value representing the mean first-order surface gradient (slope) computed across the analysis grid for the queried coordinate. Coordinates outside Hungary's Natural Earth boundary are rejected before 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-hungary-mean-first-order-surface-slope-2e3a4618/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)