Website uptime and change check: is this URL up right now, and has the page changed? Fetches the URL and returns the HTTP status, Last-Modified and ETag headers, a SHA-256 fingerprint of the content, and whether it changed versus a hash you pass in. Use it to check a site is live, detect stale data, monitor a page for changes, or decide whether to invalidate a cache before your agent acts on what it says. Returns a signed attestation.

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