URL Health Check - is this endpoint actually alive?

Given a public URL, returns a measured verdict - LIVE, PAUSED, DEGRADED, GATED, DOWN, DEAD, UNKNOWN - with the reason and the surface it was read from, not just an HTTP status code. Catches the case a status check misses: a front door answering 200 over a backend that has stalled. Reads the origins own /health, /healthz or /status when it publishes one, including a stale heartbeat field (last_heartbeat, updated_at, ts...) even when its status field still says ok. Checks robots.txt before probing (a disallow is reported as GATED, never bypassed). Parses x402 payment terms when the URL answers 402. A genuine timeout is reported UNKNOWN rather than forced into DEAD - a slow origin and a dead one are not the same evidence. Identifies itself truthfully via User-Agent, GET only, no credential ever sent, private/loopback/link-local/cloud-metadata targets refused before any request. GET /at-check?url=... or POST {"url": "..."}. First 3 calls free. Need several URLs at once? See our batch listing (up to 10 per call).