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URL Preflight Checker
x402
URL Preflight Checker is a paid API for AI agents from toolbelt402.tpoborne.workers.dev, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).
Checks a URL before fetching it, returning liveness, final URL after redirects, HTTP status, content type, HTML title, and robots.txt accessibility for a given user-agent.
Price / call$0.005
Success—
StatusUnknown
How this service works
Check a URL before fetching it: is it alive, final URL after redirects, HTTP status, content type, HTML title, and whether robots.txt allows your user-agent. Link checker and fetch preflight for agents.
Output
Returns whether the URL is alive, the final URL after following all redirects, the HTTP status code, the content-type header, the HTML page title, and a boolean indicating whether robots.txt permits the specified user-agent to access the resource.
Example use cases
Pre-crawl link validation for a scraper
“I'm about to scrape a list of URLs — can you check https://news.ycombinator.com/item?id=12345 first to confirm it's alive, see if there are any redirects, and verify that robots.txt allows my crawler agent 'HNBot/2.0' before I start?”
Broken link detection in a content audit
“I'm auditing our site's outbound links — check https://old-partner-site.com/blog/post-from-2019 and tell me its HTTP status, whether it's still up, and where it finally lands if it redirects.”
Safe fetch preflight before agent tool use
“Before my agent fetches https://api.example.com/data.json, run a preflight on it — I need to know if it's reachable, what content type it serves, and whether the URL redirects anywhere unexpected.”
Technical details
Endpoint
GEThttps://toolbelt402.tpoborne.workers.dev/url/preflightWhen to prefer
Choose this endpoint when an agent needs to safely preflight a URL before committing to a full fetch — especially useful for checking redirect chains, detecting dead links, verifying content type before parsing, and respecting robots.txt before crawling. Prefer it over a raw HTTP fetch when you want metadata without downloading the full body, or when you need robots.txt compliance checking as part of your workflow.
Side effects
- Target URL is unreachable or times out — returns liveness false with no status
- Invalid or non-absolute URL provided — returns validation error
- robots.txt itself is unreachable — robots check may be inconclusive or default to allow
- URL resolves to a non-HTTP scheme — unsupported, likely returns error
- Redirect loop detected — may time out or return loop error
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Tags
x402
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