What it means
The contract between systems
An API describes available operations, inputs, outputs and error behavior. A remote HTTP API also needs rules for authentication, permissions and version compatibility. An OpenAPI description can document an HTTP interface, but is not itself the running service.
Payment integration
A reliable integration follows the provider’s contract for payment creation, status checks, notifications and recovery. HTTP status, application status and business completion can differ. A client should preserve operation identifiers and handle uncertain outcomes without assuming that a timeout means no work happened.
Related concepts
In practice
A concrete example
An online store calls a payment API to create a payment request, then checks documented status events before fulfilling the order.
Technical notes & boundaries
An API is not necessarily REST, GraphQL or public. Interface style does not automatically determine reliability, security or supported payment methods.
Go to the source.
Original references used for this definition. Product details and standards can change.
