# HALOWERK Atlantic Land – Mean Surface Slope (France)

> HALOWERK Atlantic Land – Mean Surface Slope (France) is a paid API for AI agents from atlantikland.halowerk.com, paid per call via x402, $0.003/call, status unknown (last checked 2026-09-15).

Returns the mean first-order surface gradient (slope) across an analysis grid cell for a given coordinate within France, validated against Natural Earth boundaries.

## Facts

- Endpoint: POST https://atlantikland.halowerk.com/v1/fr-mean-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-atlantic-land-mean-surface-slope-france-38d7920e
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_fsFd6GIYhVhMSoigc9R1z

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-atlantic-land-mean-surface-slope-france-38d7920e -d '<json body>'
```

Example prompt: What's the mean surface slope at latitude 43.7° N, longitude 3.5° E in France — I need the terrain gradient for a land assessment there.

## When to prefer this

Choose this endpoint when you need a precise, grid-level mean slope value for a specific point within France, particularly for land suitability analysis, agricultural planning, civil engineering, hydrology, or environmental assessments. It is especially useful when you need boundary-validated terrain metrics and want to avoid paying for out-of-bounds queries.

## Known failure modes

- Coordinate outside France boundary — rejected before payment, returns validation error
- Coordinate outside European coverage range (lat 34–72.5, lon -31.5–40.5) — input schema validation error
- Missing or malformed latitude/longitude — returns 400 bad request
- Payment failure via x402 protocol — call not executed
- Service unavailability — returns 5xx error

## How this service works

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

## Output

A numeric value representing the mean first-order surface gradient (slope) across the analysis grid cell centred on the provided coordinate. The coordinate is pre-validated against the Natural Earth boundary for France; coordinates outside France are rejected before any charge is incurred.

## 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-atlantic-land-mean-surface-slope-france-38d7920e/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from atlantikland.halowerk.com](https://www.zero.xyz/host/atlantikland.halowerk.com/llms.txt)