# HALOWERK Central Land – Mean Surface Slope (Liechtenstein)

> HALOWERK Central Land – Mean Surface Slope (Liechtenstein) is a paid API for AI agents from mitteleuropa.halowerk.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-14).

Returns the mean first-order surface gradient (slope) across an analysis grid cell for a given coordinate within Liechtenstein.

## Facts

- Endpoint: POST https://mitteleuropa.halowerk.com/v1/li-mean-slope
- Price: $0.003/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/halowerk-central-land-mean-surface-slope-liechtenstein-bc6a2f80
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_DCc7P4Jz9BN4N9JrTINC9

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-central-land-mean-surface-slope-liechtenstein-bc6a2f80 -d '<json body>'
```

Example prompt: What is the mean surface slope at latitude 47.14, longitude 9.52 in Liechtenstein? I need the terrain gradient for a site assessment.

## When to prefer this

Use this endpoint when you need a precise, paid-per-call mean terrain slope value specifically for a coordinate within Liechtenstein, sourced from high-resolution European DEM data. Prefer this over generic elevation APIs when first-order gradient (slope) rather than raw elevation is required, and when Liechtenstein boundary enforcement is needed for data quality.

## Known failure modes

- Coordinate outside Liechtenstein boundary: request rejected with a boundary validation error before payment
- Latitude or longitude outside European coverage range (lat 34–72.5, lon -31.5–40.5): input validation failure
- Missing required latitude or longitude fields: request fails with schema validation error
- DEM data unavailable for the requested grid cell: returns an error indicating no data
- Payment failure via x402 protocol: call 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 Liechtenstein; results outside it are rejected before payment.

## Output

Returns the mean first-order surface gradient (slope) value computed across the analysis grid for the specified coordinate. Coordinates outside the Liechtenstein Natural Earth boundary are rejected before any charge is applied.

## 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-central-land-mean-surface-slope-liechtenstein-bc6a2f80/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from mitteleuropa.halowerk.com](https://www.zero.xyz/host/mitteleuropa.halowerk.com/llms.txt)