Verify a seller x402 endpoint with a signed receipt

SELLER-SIDE endpoint verification with a portable signed receipt. Probes your x402 surface (discovery docs, unpaid-402 conformance, wash screen on each resolved payTo) and returns an Ed25519 AgentReadinessReceipt of what was observed - including a failing result. The payment buys the work and the artifact, never the verdict: basis is endpoint_conformance and not_a_trust_vouch is always true, so a 'ready' card is not a recommendation to pay the seller and does not affect any ranking. Free unsigned equivalent: POST /v1/agent-readiness. Verify offline with npm/PyPI twzrd-receipt-verifier. x402-paid: 0.05 USDC (50000 base units) on Solana mainnet. Path A: bind to the accepts[] entry whose extra.feePayer you intend to pay; settle-rail settlement requires that feePayer to match GET /supported.