# Kairostamp Receipt Verification

> Kairostamp Receipt Verification is a paid API for AI agents from kairostamp.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-16).

Verifies an existing Kairostamp receipt by recomputing its SHA-256 digest, checking hash-chain linkage to the preceding entry, and reporting whether it is covered by an on-chain checkpoint.

## Facts

- Endpoint: GET https://kairostamp.com/api/v1/verify
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/kairostamp-receipt-verification-11ab6e11
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_MymTSKE35jOVD8-m810Qy

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-receipt-verification-11ab6e11
```

Example prompt: Can you verify Kairostamp receipt 85cd424c-b68b-440e-8f4f-e02147799f30 and tell me whether it's valid, properly linked in the hash chain, and covered by an on-chain checkpoint?

## When to prefer this

Use this endpoint when you need to cryptographically verify the integrity of a receipt previously issued by a Kairostamp paid endpoint, without making any external network requests. It is the canonical tamper-detection tool for Kairostamp receipts, checking both the local hash-chain linkage and on-chain anchor coverage in a single lightweight GET call. Prefer it over manual digest recomputation or external blockchain explorers for Kairostamp-specific receipts.

## Known failure modes

- Receipt ID does not exist in the system — exists: false, verdict: indeterminate
- Malformed or non-UUID receipt_id — HTTP 400 or validation error
- Receipt hash mismatch — verdict: invalid indicating possible tampering
- No on-chain checkpoint yet — anchor.covered: false with explanatory note
- Legacy receipt with incompatible format — verdict: quarantined_legacy

## How this service works

Receipt verification: read-only hash-chain verification of one existing Kairostamp receipt id. Recomputes the canonical SHA-256 digest, compares it with the stored chain hash, checks linkage to the preceding entry and reports whether the entry is covered by an on-chain checkpoint. Performs no outbound fetch. Single GET query parameter (receipt_id).

## Output

Returns a JSON object containing the receipt UUID, a boolean indicating whether it exists, a verdict enum (valid, invalid, indeterminate, or quarantined_legacy), chain details (sequence number, chain hash, previous chain hash, and a linked boolean), and an anchor object indicating whether an on-chain checkpoint covers this entry along with network and status details where available.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/kairostamp-receipt-verification-11ab6e11/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)