All the events and business unit available fields are documented Attributes documentation

List of errors

All errors will follow this pattern :

{
    "message": "You don't have the permission to perform this action",
    "status": 403,
    "data": {
        ...
    }
}

You will often find more details in the data object and when there are several errors on a bulk update, you will find the list of errors in the errors array.