# Kairostamp

> Paid machine-to-machine web evidence API. Fetches one public http/https URL server-side and returns a time-stamped, tamper-evident receipt; the change-check endpoint also compares it against a caller-supplied baseline.

No accounts, no API keys, no subscriptions. Each call is paid individually with
x402 (exact USDC on base).
Call an endpoint without payment to receive a 402 with machine-readable terms.

## Free trial

One free call per wallet address, on any GET endpoint below.
Claim: POST https://kairostamp.com/api/public/trial with {"wallet": "0x..."}.
Redeem: send the returned token as the X-Kairostamp-Trial header. No account, no signature.

## Endpoints

- [snapshot](https://kairostamp.com/api/v1/snapshot): POST, $0.05 per call. Kairostamp evidence snapshot: server-side fetch of one public http/https URL, returning a time-stamped receipt with the response status, content type, byte length, SHA-256 of the body, redirect chain, a text preview, and a tamper-evident hash-chain entry.
- [change_check](https://kairostamp.com/api/v1/change-check): POST, $0.05 per call. Kairostamp change check: server-side fetch of one public http/https URL, compared against a baseline the caller already holds.
- [digest](https://kairostamp.com/api/v1/digest): GET, $0.01 per call. URL digest receipt: server-side fetch of one public http/https URL, returning a time-stamped receipt with the HTTP status, final URL, content type, byte length, SHA-256 of the response body, redirect chain, receipt id and tamper-evident hash-chain entry.
- [headers](https://kairostamp.com/api/v1/headers): GET, $0.005 per call. URL HTTP metadata receipt: server-side fetch of one public http/https URL, returning only transport metadata — HTTP status, final URL, redirect chain, content type and byte length — plus a receipt id.
- [verify](https://kairostamp.com/api/v1/verify): GET, $0.005 per call. Receipt verification: read-only hash-chain verification of one existing Kairostamp receipt id.
- [robots_check](https://kairostamp.com/api/v1/robots-check): GET, $0.005 per call. robots.txt check: fetches the origin's /robots.txt server-side and reports whether a given URL path is allowed or blocked for a user agent, with the matched rule, the robots URL, the HTTP status, a timestamp and a tamper-evident receipt.
- [redirect_audit](https://kairostamp.com/api/v1/redirect-audit): GET, $0.01 per call. Redirect audit: follows one public http/https URL server-side and returns the ordered redirect chain, hop count, final URL, final HTTP status, whether the destination changed origin and whether HTTPS was downgraded to HTTP, with a timestamp and a tamper-evident receipt.
- [text_extract](https://kairostamp.com/api/v1/text-extract): GET, $0.02 per call. Readable text extraction: fetches one public HTML page server-side and returns clean plain text with the page title, final URL, HTTP status, content type, SHA-256 of the response body, a timestamp and a tamper-evident receipt.
- [link_map](https://kairostamp.com/api/v1/link-map): GET, $0.015 per call. Link map: fetches one public HTML page server-side and returns up to 100 normalized, deduplicated http/https links with internal/external classification and counts, the final URL, a timestamp and a tamper-evident receipt.
- [sitemap](https://kairostamp.com/api/v1/sitemap): GET, $0.01 per call. Sitemap lookup: locates a site's sitemap from robots.txt or same-origin /sitemap.xml, fetches it server-side and returns up to 100 normalized http/https URLs with the sitemap URL, document kind, count, truncation flag, a timestamp and a tamper-evident receipt.

## Machine-readable

- [Discovery document](https://kairostamp.com/api/public/discovery)
- [OpenAPI](https://kairostamp.com/openapi.json)
- [Agent card](https://kairostamp.com/.well-known/agent-card.json)
- [x402 index](https://kairostamp.com/.well-known/x402)
- [MCP server, streamable HTTP](https://kairostamp.com/mcp)

## Policies

- [Documentation](https://kairostamp.com/docs)
- [Terms](https://kairostamp.com/terms)
- [Acceptable use](https://kairostamp.com/acceptable-use)
- [Refunds](https://kairostamp.com/refunds)
- [Privacy](https://kairostamp.com/privacy)

No uptime, availability, legal or compliance guarantee is made.