# HALOWERK Baltic Land – Mean Surface Slope (Poland)

> HALOWERK Baltic Land – Mean Surface Slope (Poland) 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 coordinate validated against Poland's boundary.

## Facts

- Endpoint: POST https://baltikum.halowerk.com/v1/pl-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-mean-surface-slope-poland-44d5b085
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_ILc_nVovcAciyQ7uvwFJQ

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-mean-surface-slope-poland-44d5b085 -d '<json body>'
```

Example prompt: What's the mean surface slope at latitude 52.23, longitude 21.01 in Poland? I need the average terrain gradient for that location.

## When to prefer this

Choose this endpoint when you need a mean surface slope value for a specific point within Poland and want coordinate boundary validation (non-Polish coordinates are rejected before payment). It is ideal for applications requiring terrain gradient data for Polish territory such as agricultural suitability, infrastructure planning, or erosion modeling, and when integrated with other HALOWERK Baltic Land endpoints (max slope, ruggedness, land cover) for composite terrain analysis.

## Known failure modes

- Coordinate outside Poland boundary — rejected before payment with a validation error
- Latitude or longitude outside the European coverage range (lat 34–72.5, lon -31.5–40.5) — request rejected
- Missing or malformed latitude/longitude fields — schema validation error
- Coordinate within European range but outside Poland boundary — boundary check failure before charge
- Service unavailability — HTTP 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 Poland; results outside it are rejected before payment.

## Output

A numeric value representing the mean first-order surface gradient (slope) computed across the analysis grid cells surrounding the queried coordinate within Poland. Coordinates outside the Poland boundary are rejected before any computation or 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-baltic-land-mean-surface-slope-poland-44d5b085/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)