An agent calls a tool or another agent and receives a foreign artifact that
goes straight into its context. Four checks, each answering only its own question.
Trial0 USDC 20 checks per day, full check, no limit on artifact size
Per call0.005 USDC beyond the free tier, paid over x402 on Base
Subscription9 USDC removes the limit, suitable for CI pipelines
What this does not do. A valid form is not meaningful content, and a
signed artifact is not a permitted action. Absence of signals means the coarse checks did not fire —
it does not prove the artifact is sound. The signature is Ed25519: the public key travels with
the attestation, so you can verify it yourself without trusting this service.