# Forest Gas Station – Service State Change Detection

> Forest Gas Station – Service State Change Detection is a paid API for AI agents from http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-01).

Checks whether a remote service's current state has materially changed since a previously recorded canonical hash, acting as a cheap watchdog.

## Facts

- Endpoint: POST https://http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run/service/changed?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-01
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/forest-gas-station-service-state-change-detection-f7e0ff08
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_UBQeqwM_spWWXxwJjnfgL

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 forest-gas-station-service-state-change-detection-f7e0ff08 -d '<json body>'
```

Example prompt: Check if the service at https://api.example.com/status has changed since the last time I polled it — the previous hash was a3f7b2c1d4e5 — and tell me if anything material is different now.

## When to prefer this

Choose this endpoint when you need a lightweight, cheap ($0.001) way to detect whether a service's state has materially changed without parsing or deeply analyzing the full response — ideal for polling loops, pre-action checks, and drift detection. Prefer it over full scraping or status-page parsers when you only need a boolean changed/unchanged signal plus a hash for future comparisons.

## Known failure modes

- status_url is unreachable or returns a non-2xx response, causing the probe to fail
- previous_hash format exceeds 128 characters, rejected by schema validation
- service returns inconsistent or non-deterministic content making hash comparison unreliable
- network timeout when probing the target URL
- malformed status_url causes request failure

## How this service works

Cheap watchdog: material service state changed since prior canonical hash? Base mainnet USDC

## Output

A response indicating whether the service at the given URL has materially changed since the provided previous hash, along with the current canonical hash of the service state for future comparisons. If no previous hash is supplied, the current hash is returned as a baseline.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "status_url": {
   "type": "string",
   "description": "Public status url value used to scope this lookup."
  },
  "previous_hash": {
   "type": [
    "string",
    "null"
   ],
   "maxLength": 128,
   "description": "Earlier result hash used to detect a material change."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/forest-gas-station-service-state-change-detection-f7e0ff08/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run](https://www.zero.xyz/host/http--forest-gas-station-mainnet--lcjl27p8lmjs.code.run/llms.txt)