# HALOWERK Baltic Land – Lithuania Mean First-Order Surface Gradient

> HALOWERK Baltic Land – Lithuania Mean First-Order Surface Gradient 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 slope gradient across an analysis grid for a given coordinate within Lithuania, validated against the Natural Earth boundary.

## Facts

- Endpoint: POST https://baltikum.halowerk.com/v1/lt-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-lithuania-mean-first-order-surface-gradient-33e33bec
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_KzXJbThniNZamATTh6000

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-lithuania-mean-first-order-surface-gradient-33e33bec -d '<json body>'
```

Example prompt: What is the mean surface slope gradient at latitude 54.6872, longitude 25.2797 in Lithuania? I need the first-order terrain steepness for that point.

## When to prefer this

Use this endpoint when you need the average slope steepness (first-order gradient) at a specific point within Lithuania and want boundary validation before incurring payment costs. Prefer this over maximum-slope or ruggedness endpoints when a smoothed, mean gradient is needed for land suitability, hydrology, or infrastructure planning rather than worst-case terrain values.

## Known failure modes

- Coordinate outside Lithuania boundary — request rejected before payment, with a boundary validation error
- Coordinate outside European coverage range (lat 34–72.5, lon -31.5–40.5) — schema validation failure
- Missing or malformed latitude/longitude fields — input validation error
- Server-side computation failure for sparse elevation data — internal error response

## How this service works

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

## Output

A numeric value representing the mean first-order surface slope gradient across the analysis grid cell at the requested coordinate. Coordinates outside the Lithuanian boundary are rejected before 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-lithuania-mean-first-order-surface-gradient-33e33bec/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)