# HALOWERK Europe Land – Mean Surface Slope (Parcel Polygon)

> HALOWERK Europe Land – Mean Surface Slope (Parcel Polygon) is a paid API for AI agents from euroland.halowerk.com, paid per call via x402, $0.006/call, status unknown (last checked 2026-09-15).

Computes the mean first-order surface slope gradient across a user-supplied WGS84 polygon parcel, returning standardized units for any of 30 European countries.

## Facts

- Endpoint: POST https://euroland.halowerk.com/v1/europe-mean-slope-parcel
- Price: $0.006/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/halowerk-europe-land-mean-surface-slope-parcel-polygon-33376625
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8jTn639dDg6yOMKYjDxum

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-europe-land-mean-surface-slope-parcel-polygon-33376625 -d '<json body>'
```

Example prompt: What is the mean slope gradient of this parcel in Bavaria — the polygon is roughly bounded by coordinates (11.2, 48.1), (11.25, 48.1), (11.25, 48.15), (11.2, 48.15)?

## When to prefer this

Choose this endpoint when you need a single aggregated slope metric for a custom polygon parcel anywhere across 30 European countries, especially for agricultural, environmental, or land development use cases. Prefer it over raster downloads when you want a ready-to-use scalar value without post-processing. If you need aspect/orientation (south-facing index) or land cover shares rather than raw slope, use the sibling endpoints on the same platform.

## Known failure modes

- Polygon spans more than 0.25 degrees — request rejected with validation error
- Fewer than 3 coordinate pairs provided — invalid polygon error
- Coordinates fall outside the European coverage area (lat 34–72.5, lon -31.5–40.5) — out-of-coverage error
- Polygon array items with incorrect coordinate ordering or extra items — schema validation failure
- Payment not provided or insufficient — x402 payment required response

## How this service works

Mean first-order surface gradient across the analysis grid. The service evaluates the bounded polygon supplied by the caller and returns standardized units across all 30 covered countries.

## Output

A single standardized numeric value representing the mean first-order surface slope gradient across all pixels within the supplied polygon, expressed in consistent units applicable across all 30 covered European countries.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "polygon": {
   "type": "array",
   "items": {
    "type": "array",
    "items": [
     {
      "type": "number",
      "maximum": 40.5,
      "minimum": -31.5
     },
     {
      "type": "number",
      "maximum": 72.5,
      "minimum": 34
     }
    ],
    "maxItems": 2,
    "minItems": 2,
    "additionalItems": false
   },
   "maxItems": 100,
   "minItems": 3,
   "description": "WGS84 polygon ring. The closing coordinate is optional; maximum span is 0.25 degrees."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/halowerk-europe-land-mean-surface-slope-parcel-polygon-33376625/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from euroland.halowerk.com](https://www.zero.xyz/host/euroland.halowerk.com/llms.txt)