Basic information
All API requests must use HTTPS access endpoints as follows:

Endpoint	Environment	Notes
https://open-fat.cb.paykka.com	Sandbox
	Production	Apply offline

#Data format

JSON is used as the request/response body format

Required headers:

Note: File upload APIs are exceptions

Parameter compatibility

Request success is independent of parameter order

Request success is independent of JSON key order

Do not assume response JSON key order when parsing

New API versions may:

Add new parameters or JSON fields

New API versions will NOT:

Remove existing required parameters or fields

Null values in request/response JSON may be omitted

#Character encoding
UTF-8 must be used for request/response bodies

Time format

All timestamps must follow ISO 8601
Timezone must be UTC (suffix "Z")

Message example:

{
  "date": "2023-12-04T23:25:59Z"
}

The above represents:
UTC: 2023-12-04 23:25:59
Beijing Time (UTC+8): 2023-12-05 07:25:59

HTTP Status Codes

Status code	Description
200	Request processed successfully
4xx	Request failed due to client error (invalid format, missing parameters, invalid state, insufficient balance, etc.)
5xx	Server error (network issue, system defect, etc.)

When a request fails, the response body includes detailed error information:

Key	Type	Description
ret_code	String(6)	Error code
ret_msg	String	Error message

Error code	Description
999999	Unknown error (contact support)
010000	Invalid request parameters (format error / missing fields)
010001	Too many requests
010002	Data not found
010003	Invalid data state
010004	Data integrity violation
010005	File size exceeds limit
010100	Unauthorized request (signature verification failed)
010200	Unauthorized request (signature verification failed)