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Livecheck Sentinel One-Shot Check
x402
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.
Price / call$0.02
Success—
StatusUnknown
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.
Example use cases
Verify job listing still active
“Before I apply, can you check if this Greenhouse job posting is still live? The URL is https://boards.greenhouse.io/acmecorp/jobs/9921 — use a status_change detector, no baseline hash since this is my first check.”
Detect price drop below threshold
“Check the product page at https://shop.example.com/products/sneaker-x and tell me if the price is now below $89 — use a numeric_threshold detector with the CSS selector .product-price.”
Keyword presence check on webpage
“Look at https://techcrunch.com/2024/03/funding-roundup and tell me whether the word 'Series B' appears anywhere on the page — use a keyword detector.”
Technical details
Endpoint
POSThttps://livecheck.fly.dev/v1/checkWhen to prefer
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.
Side effects
- 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
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| target | object | URL target. type=url, render=never. selector optional. |
| condition | object | 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 | — | Prior observation.hash for status_change. Omit or null on first check. |
Output
Schema · Response
{
"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"
}
}
}Tags
x402
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