JSON

Outcome: Design or review JSON for this system while keeping data correct, secure, and easy to operate. User context: A payment service sends `{"amount":2400,"currency":"TWD"}` as UTF-8 and checks it against a contract. A 19-digit invoice ID is sent as text because some systems cannot store that number exactly. Data with the same member name twice is rejected. Technical concept or control: JSON. Why it fits: Use JSON for structured data when both sides agree on field types and whether `null` is allowed. They must also agree on number limits and version rules. Do not use it when: JSON is not a schema. Standard JSON does not allow comments or `NaN`, and object member order has no meaning. Engineering requirements: Define inputs, outputs, contracts, and rules that must always hold. Set authorization and input checks. Define failures, timeouts, retries, one-time effects, data moves, and compatibility limits. Operations: Add useful signals and logs that hide sensitive data. Set capacity limits and write an operator guide. Test recovery and rollback. Acceptance criteria: Contract and failure-path tests pass. Data and authorization rules still hold during retries and partial failures. Check performance limits, monitoring, recovery, and rollback. Evidence and limits (evidence boundary): The standard covers only the listed scope. It does not choose the visual style, product decision, or Vibulary example. Unknowns to confirm: Where the code runs, data stores, traffic shape, consistency needs, and the security boundary. Also confirm the compatibility period, service goals, and rollback limits.