FAQ — x402 payment failures and MAKO receipts
Answers are drawn from the frozen claims taxonomy v1.0.0 and GUARD receipt spec v1.0.0; those documents are normative.
What is a MAKO GUARD receipt?
An EIP-712-signed record emitted for every payment-bearing request to a MAKO x402 route. It binds the request hash, response hash, quoted and settled USDC amounts, settlement transaction hash, and payer address into one verifiable document. The format is frozen as receipt spec v1.0.0.
How do I verify a MAKO receipt is authentic?
Three rules, all required: (1) the receipt_id recomputes from the receipt body; (2) the EIP-712 signature recovers to the receipt's signer; (3) that signer holds a validity window in the published append-only signer registry covering the receipt's timestamp_response_ms. The frozen spec contains the exact type array and exclusion rules.
What counts as non-delivery in an x402 payment?
Payment settled but no response returned: settlement evidence exists for the receipt and no response hash was recorded within the delivery timeout. In the taxonomy this is NON_DELIVERY — critical severity, deterministic detection, default resolution refund.
Is a settlement failure refundable?
No. SETTLEMENT_FAILURE means settlement failed after the service already delivered its response — the buyer was never charged, so there is nothing to refund. It is recorded as a failure event but is never claimable.
When is a latency breach claimable?
Only when the endpoint declares an SLA. LATENCY_BREACH compares the receipt's request and response timestamps against the declared maximum latency; with no declared SLA there is no contract to breach, and the claim is rejected at filing. MAKO's own routes all declare SLAs.
What is the difference between an overcharge and a duplicate charge?
OVERCHARGE is one settlement whose on-chain amount exceeds the quoted amount. DUPLICATE_CHARGE is more than one settlement transaction mapping to the same request (the same payment payload). Both are deterministic from receipt evidence and both default to refund.
Which failure events can a buyer claim?
Six: NON_DELIVERY, MALFORMED_RESPONSE, LATENCY_BREACH, OVERCHARGE, DUPLICATE_CHARGE, and SILENT_FAILURE. Malformed-response and latency-breach claims additionally require the endpoint to declare a response schema or SLA respectively. SETTLEMENT_FAILURE is recorded but never claimable.
Do MAKO's own test transactions appear in public statistics?
No. MAKO's own traffic — self-calls and synthetic tests — is labeled at the ledger level and excluded from every public statistic.
Where are the frozen specifications and how do I check their hashes?
Taxonomy (raw JSON at /specs/taxonomy-v1.json) and receipt spec (raw text at /specs/receipt-spec-v1.md). Download the raw file and run shasum -a 256; the hash printed on the page must match.