# HALOWERK Baltic Land — Estonia Mean Surface Slope

> HALOWERK Baltic Land — Estonia Mean Surface Slope is a paid API for AI agents from baltikum.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 the analysis grid for a given WGS84 coordinate within Estonia.

## Facts

- Endpoint: POST https://baltikum.halowerk.com/v1/ee-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-baltic-land-estonia-mean-surface-slope-53b673ee
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_y88b5idmNM8ZqpnGobtcH

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-baltic-land-estonia-mean-surface-slope-53b673ee -d '<json body>'
```

Example prompt: What's the mean surface slope at latitude 58.37, longitude 26.72 in Estonia? I need the average terrain gradient for that location.

## When to prefer this

Choose this endpoint when you need the mean first-order surface slope specifically for a coordinate within Estonia, particularly when boundary validation is required before processing. It is ideal for land suitability, environmental risk, infrastructure planning, or any application that requires a reliable, pre-validated terrain gradient value for Estonian locations. Prefer it over general-purpose elevation APIs when you specifically need slope (gradient) rather than raw elevation, and when operating within Estonia.

## Known failure modes

- Coordinate outside Estonia boundary — request rejected before payment with a validation error
- Coordinate outside the broader European coverage window (lat 34–72.5, lon -31.5–40.5) — rejected at schema validation
- Missing or malformed latitude/longitude — returns a 400-level error
- Payment failure via x402 protocol — call not executed

## How this service works

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

## Output

A numeric value representing the mean first-order surface gradient (slope) across the analysis grid centered on the requested coordinate, validated to lie within the Estonia boundary. Requests for coordinates outside Estonia are rejected before any charge is made.

## 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-baltic-land-estonia-mean-surface-slope-53b673ee/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from baltikum.halowerk.com](https://www.zero.xyz/host/baltikum.halowerk.com/llms.txt)