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Watch & Diff — HTTP Headers Fetch
x402
Watch & Diff — HTTP Headers Fetch is a paid API for AI agents from watch-diff.agent-utils.workers.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).
Fetches the HTTP response headers for a given URL, returning status, redirect info, timing, and all headers without downloading the full body.
Price / call$0.005
Success—
StatusUnknown
How this service works
Did this URL change since my last check? Fetch, normalize, hash and diff any page, region or JSON for AI agents running recurring tasks. State per paying wallet, 90 days. Pay per call over x402, no API key.
Output
A JSON object with: ok (boolean), url (the requested URL), status (HTTP status code), headers (key-value map of all response headers such as ETag, Last-Modified, Cache-Control, Content-Type, Server), finalUrl (URL after any redirects), redirected (boolean), checkedAt (ISO timestamp), and responseMs (round-trip latency in milliseconds).
Example use cases
Cache freshness check for a resource
“Check the headers for https://api.partner.com/feed.json — I want to know the Cache-Control policy, the ETag, and whether it redirected before answering.”
Uptime and redirect monitoring
“Probe https://myapp.com/health right now and tell me if it returned a 200 or redirected, how long it took, and what server header it reported.”
Content-type verification before processing
“Before I send that URL to my pipeline, can you fetch the headers for https://cdn.example.com/report.pdf and confirm the content-type and content-length so I know it's actually a PDF?”
Technical details
Endpoint
GEThttps://watch-diff.agent-utils.workers.dev/v1/headersWhen to prefer
Use this endpoint when you only need HTTP metadata (headers, status, redirect chain, latency) for a URL without downloading and parsing the full body. It is ideal for lightweight change detection using ETag or Last-Modified, uptime probing, content-type pre-checks, and redirect auditing. Prefer it over full-page fetch or diff endpoints when you do not need body content. It charges per call via x402 micropayments with no API key setup required.
Side effects
- URL is unreachable or DNS fails — returns ok: false with an error message
- URL exceeds 2 MB body limit — may error or truncate
- Non-HTTP/HTTPS URLs are rejected
- Payment via x402 fails or wallet has insufficient USDC — request is rejected before fetch
- Target server returns no headers or times out — partial or error response
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"ok": true,
"url": "https://example.com/",
"status": 200,
"headers": {
"etag": "\"8423…\"",
"server": "ECAcc",
"content-type": "text/html; charset=UTF-8",
"cache-control": "max-age=3600",
"last-modified": "Mon, 13 Jan 2025 20:11:20 GMT",
"content-length": "1256"
},
"finalUrl": "https://example.com/",
"checkedAt": "2026-09-06T21:10:00.000Z",
"redirected": false,
"responseMs": 95
}
}Tags
x402
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