Data Notary (timestamp proof) ($0.002/call)

Prove a piece of data existed at a point in time. POST {data} returns its sha256, a recorded timestamp, and an HMAC receipt; GET ?hash= tells you whether and when that hash was first notarized. An agent can hash data but cannot self-certify WHEN it existed to a third party — this is that proof.

Paid endpoint: $0.002 per call via the x402 protocol (USDC on Base). An unpaid request returns 402 with payment requirements in the PAYMENT-REQUIRED response header; attach payment and retry.