# Kairostamp URL Digest Receipt

> Kairostamp URL Digest Receipt is a paid API for AI agents from kairostamp.com, paid per call via x402, $0.002/call, status down (last checked 2026-10-13).

Fetches a public URL server-side and returns a tamper-evident receipt containing HTTP status, final URL, content type, byte length, SHA-256 hash, redirect chain, and a hash-chain entry for audit integrity.

## Facts

- Endpoint: GET https://kairostamp.com/api/v1/digest?utm_source=zero.xyz
- Price: $0.002/call
- Payment: x402
- Status: down
- Last checked: 2026-10-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/kairostamp-url-digest-receipt-afc6e8ea
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_NG7d5TTnx0rF-MO-8i6p_

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability kairostamp-url-digest-receipt-afc6e8ea
```

Example prompt: Fetch https://example.com/contract.pdf and give me a tamper-evident digest receipt — I need the SHA-256 hash, HTTP status, byte length, and a hash-chain entry I can use as evidence.

## When to prefer this

Choose this endpoint when you need a single-point-in-time cryptographic attestation of what a URL served — combining HTTP metadata, body hash, and a tamper-evident hash chain — rather than just checking liveness or extracting readable content. Prefer it over the sibling HTTP metadata endpoint when you need the SHA-256 body hash and hash-chain linkage for audit or legal purposes. Use it when the goal is to create verifiable evidence of a URL's content that can be independently verified via Kairostamp's receipt verification endpoint.

## Known failure modes

- Non-public or authenticated URLs return an error since the server fetches without credentials
- Unreachable or offline URLs result in a connection error receipt
- URLs exceeding 2048 characters are rejected by schema validation
- Private/intranet URLs (e.g. localhost, 192.168.x.x) are likely blocked
- Malformed URL format returns a 400-level validation error
- Very large response bodies may time out or be truncated

## How this service works

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. Single GET query parameter (url). One call performs one fetch; there is no monitoring and no retry.

## Output

Returns a JSON object containing: a UUID receipt_id, a fetched_at ISO timestamp, the final URL after redirects, HTTP status_code, content_type, byte_length, sha256 hash of the response body, an ordered redirect_chain array, an optional text_preview, a chain_hash (SHA-256 hash-chain entry linking this receipt to prior ones), and a previous_chain_hash for chain continuity verification.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/kairostamp-url-digest-receipt-afc6e8ea/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from kairostamp.com](https://www.zero.xyz/host/kairostamp.com/llms.txt)