HTTP Status	Error	Description
400 Bad Request	Validation error	Invalid request payload, including: • missing required fields • invalid field types or formats • `price_amount` not a positive number • unsupported `price_currency` • duplicate `order_id` for the same merchant
401 Unauthorized	`Unauthorized`	Missing or invalid authentication (Bearer token or session)
429 Too Many Requests	`Rate limit exceeded, retry in 2 minutes`	API rate limit exceeded

{
  "error": "Error message"
}

{
  "statusCode": 429,
  "error": "Too Many Requests",
  "message": "Rate limit exceeded, retry in 2 minutes"
}