# Livecheck Sentinel One-Shot Check

> Livecheck Sentinel One-Shot Check is a paid API for AI agents from livecheck.fly.dev, paid per call via x402, $0.02/call, status unknown (last checked 2026-09-15).

Performs a single on-demand URL condition check using a configurable detector (status_change, keyword, text_diff, or numeric_threshold) and returns the current observation plus whether the condition fired.

## Facts

- Endpoint: POST https://livecheck.fly.dev/v1/check
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/livecheck-sentinel-one-shot-check-d5748e8a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap__GeWyHs-9LJaB3yY3jYL1

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 livecheck-sentinel-one-shot-check-d5748e8a -d '<json body>'
```

Example prompt: Check whether the job posting at https://boards.greenhouse.io/exampleco/jobs/1842 is still live right now — use a status_change detector and compare against baseline hash abc123def456.

## When to prefer this

Use this endpoint when you need a single, immediate, one-off check of a URL condition without creating a persistent watcher. Prefer it over /v1/watch when you only need to know the current state right now (e.g., before scraping, before applying to a job, before placing an order). Use it instead of /v1/verify ($0.01) when you need richer observation signals, confidence scoring, and detector logic beyond simple existence checks. It is the right choice when your agent needs to decide whether to proceed based on a live URL condition at this moment.

## Known failure modes

- Target URL is unreachable or returns a non-2xx status — observation reflects the error state
- Invalid detector type provided — API returns a validation error
- baseline_hash format is malformed — API rejects the request
- CSS selector or jsonpath does not match any element on the page — numeric_threshold or text_diff may fail or return low confidence
- Payment not received or insufficient — x402 payment required error before check is performed
- Network timeout fetching the target URL — check returns an error observation

## How this service works

Livecheck Sentinel check - one-shot URL condition check. POST /v1/check with {target, condition, baseline_hash?}. Detectors: status_change, keyword, text_diff, numeric_threshold. Returns current observation + fired when comparable. Fixed $0.02 USDC. No watcher created. Not /v1/verify ($0.01) and not Confirm.

## Output

Returns a JSON object with a unique check ID, the fired flag (null if condition was not met, otherwise details), an observation block with HTTP status class, canonical URL, human-readable summary, extracted signals, confidence score, checked_at timestamp, and an observation hash for future baseline comparisons. Also includes a receipt with a verify URL for payment confirmation.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "target": {
   "type": "object",
   "description": "URL target. type=url, render=never. selector optional."
  },
  "condition": {
   "type": "object",
   "description": "detector status_change, keyword, text_diff, or numeric_threshold. text_diff: selector?, ignore[], min_change_ratio. numeric_threshold: selector or jsonpath, op, value, currency?"
  },
  "baseline_hash": {
   "type": [
    "string",
    "null"
   ],
   "description": "Prior observation.hash for status_change. Omit or null on first check."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "id": "chk_01J8Z0K3N4P5Q6R7S8T9V0WCHK",
  "fired": null,
  "target": {
   "url": "https://boards.greenhouse.io/example/jobs/1842",
   "type": "url",
   "render": "never",
   "selector": null
  },
  "receipt": {
   "hash": "dddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddddd",
   "verify_url": "https://livecheck.fly.dev/v1/receipt/chk_01J8Z0K3N4P5Q6R7S8T9V0WCHK"
  },
  "condition": {
   "params": {},
   "detector": "status_change"
  },
  "price_usd": 0.02,
  "confidence": 0.82,
  "observation": {
   "hash": "cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc",
   "title": "Staff Backend Engineer — Northwind Labs",
   "status": "live",
   "signals": [
    "apply form present",
    "no closure banner"
   ],
   "summary": "live 2xx (200); apply form present, no closure banner",
   "checked_at": "2026-09-10T18:00:00Z",
   "http_class": "2xx",
   "http_status": 200,
   "canonical_url": "https://boards.greenhouse.io/example/jobs/1842"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/livecheck-sentinel-one-shot-check-d5748e8a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from livecheck.fly.dev](https://www.zero.xyz/host/livecheck.fly.dev/llms.txt)