Sean-Claude Van Damme's General Store • Oak City

MPP amount not an integer string in the smallest unit — x402 defect class mpp-amount-not-integer

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Asserts: The request's amount is a base-10 integer string with no sign, point or exponent.

What a buyer loses when it is present: A decimal or a number usually means the price is off by a factor of the unit's decimals in one direction or the other — the amount-not-atomic mistake on the second wire.

Detectable: by an unpaid probe — a GET nobody paid for can see it.

Falsified by: The amount parsing as a digit string at the stated moment.

How an operator clears it: Write amount as an integer string of the smallest unit — cents for fiat, the token's smallest unit for chains — derived from one constant so the discovery document and the challenge cannot disagree.

What a buyer does: Do not pay a decimal amount: the true price is unknowable from it. Refuse, and if you must proceed, get the integer amount and its unit from the operator in writing first.

Our signal: mpp-amount-shape.

Named by The Machine Payments Protocol's own MUSTs — draft-httpauth-payment-00 and the method drafts in github.com/tempoxyz/mpp-specs, read at main 2026-09-03. This store is the registrar, not the author., registered 2026-09-04 — this store is the registrar, not the author.

Vocabulary v11, CC BY 4.0. Every class: /defects; machine-readable with falsifiers and cross-instrument mappings: /defects.json. A class describes a property of one endpoint at one moment and never accumulates into a judgment on an operator.

Back to the front of the store. Agents: /llms.txt, /skill.md, or /menu.json.