Endpoint

Task: Prove to a third party that a payment actually settled on chain. Returns: A signed JSON observation of one transaction on Base, Polygon, or Solana — the identifier's shape picks the chain — with status (SETTLED, NOT_FOUND, PENDING_FINALITY, INSUFFICIENT_MATCH or REVERTED), block height (slots on Solana), confirmations, chain head, the query echoed back, and an evidence hash — verifiable against the store's published key without asking the store. Instant. Price: $0.004 USDC (x402 v2; network from the current quote). Latency: delivered in the purchase response, same request. Verify: GET /api/verify/{id} — free, unlimited, forever (live sample: cert_4dww28dx5j). Constraints: Give the transaction in the tx_hash query parameter: an EVM hash (0x + 64 hex, read on Base and then Polygon) or a Solana signature (base58) — the shape picks the rail; Optional narrowing: payer, recipient, nonce (EVM rails only — refused beside a Solana signature), amount_usdc, or payment_payload (the base64 PAYMENT-SIGNATURE you sent, read with the store's own replay-guard code). The artifact's binding field says what the answer ties the transaction to: one uniquely identified authorizer/nonce and its paired canonical USDC Transfer bind it to one authorization, never to one request. Supply payer to distinguish reused nonces across authorizers; every supplied transfer field must match the same pair. Unrecognised event ordering establishes no binding; Optional payment_response: the PAYMENT-RESPONSE header you received, verbatim. Received, not observed — its bytes are digested into the signature and echoed outside it, and each claimed field (transaction, network, payer, success) is set beside what the chain showed: agrees, disagrees, not claimed, or not observed; Observes settlement only, never delivery; One read at one moment; no polling, no retry, no second look. Settlement Attestation, An independent signed observation of whether an x402 payment settled — on Base, Polygon or Solana, and the identifier's own shape picks the rail: a 0x hash names an EVM transaction rather than a chain, so it is read on Base and then on Polygon; a base58 signature reads Solana. Give it the transaction (and optionally the payer, recipient, nonce, or amount you expected) and it reads public chain state once and signs what it found: SETTLED, NOT_FOUND, PENDING_FINALITY, INSUFFICIENT_MATCH, or REVERTED. Produced automatically, with no human in the loop, because a party to a payment cannot produce a neutral observation of one. It observes a moment on chain: it does not attest that anything was delivered, does not promise a NOT_FOUND will never settle, and resolves no dispute.

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