Errors

Errors follow RFC 9457 problem details, always as JSON:

{
  "type": "https://business.boundlesspay.com/errors/validation-error",
  "title": "Validation error",
  "status": 422,
  "detail": "currency must be one of NGN, USD, GBP",
  "code": "VALIDATION_ERROR",
  "request_id": "req_9f2b1c7a4d"
}

Branch on code, never on detail — wording can change, codes cannot. Always log request_id: it is what support needs to trace a call end to end.

The full code list is published in the specification under Problem.code, and every endpoint page lists the codes it can return.