Payment Gateway API Documentation Generator

Payment APIs are unforgiving to document badly, because every ambiguity is a chance to move the wrong amount of money. The two details that distinguish credible payment docs from generic REST docs are amount representation and idempotency. Amounts are always integers in the currency's smallest unit — cents, pence, paise — never floats, because floating-point arithmetic on money rounds in ways that fail reconciliation. This generator emits integer minor units everywhere alongside the explicit ISO currency code, so a reader is never left guessing whether 2499 means twenty-five dollars or twenty-five cents.

Webhooks are not optional in payments — they are how you learn the true outcome of an asynchronous flow. A card may require 3-D Secure, a bank debit settles hours later, and a dispute lands days after the original charge; none of those final states fit in the synchronous HTTP response. Good docs publish the event catalogue (payment.succeeded, payment.failed, refund.created, dispute.opened) up front and insist on signature verification, because a webhook endpoint that trusts unsigned payloads is a fraud vector. The generated webhook table gives integrators that catalogue immediately.

Idempotency keys deserve a section of their own, and most generated docs omit them. The contract is simple but load-bearing: a unique key on every money-moving POST lets the client retry a dropped request without double-charging, and reusing a key with a different body must fail loudly with 409 rather than silently doing the wrong thing. Pair that with a clear error table — 402 card_declined, 422 validation_error, 429 rate_limited with Retry-After — and integrators can build correct retry logic on the first read. The companion API authentication builder covers the auth half of that contract in depth.

Finally, compliance. Reducing PCI-DSS scope through tokenization — collecting card data with a hosted field so PANs never reach your servers — is the single highest-leverage architectural decision in a payments integration, and it belongs in the docs so partners build it correctly from day one. The compliance notes here summarize that good practice but are deliberately framed as a template, not advice; your real obligations depend on your processor and jurisdiction. For the surrounding REST surface, the OpenAPI documentation generator turns a full spec into a browsable reference.