Many API functions return a default error object containing two values, "code" and "message":

{
    "code": 0,
    "message": "OK"
}

Code 0 means success, codes > 0 indicate an error.
As the error codes specify very broad categories, refer to the error message for details.

Code	Meaning	Explanation
1	Generic Error	This code is used when no other error code is a good match for the encountered problem.
2	Not Allowed	The called function is not allowed to be used in the current context or application.
3	Already Exists	The function tried to create an object or entity that already exists.
4	File I/O	A read or write operation failed.
5	Wrong File Format	A read operation failed because unexpected data was found.
6	Missing Or Invalid Input	A precondition for the function was not met, a required parameter was missing or contained unexpected data, etc.
7	Aborted By User	The function was aborted by user interaction.

Note that a lot of older functions don't use this error object yet, but return an error code as a single value.
In those cases, please refer to the individual function documentation.