Add data to a Custom field on a task. You'll need to know the task_id of the task you want to update, and the universal unique identifier (UUID) field_id of the Custom Field you want to set. You can use Get Accessible Custom Fields or the Get Task endpoint to find the field_id.
Enter the task ID of the task you want to update.
Enter the universal unique identifier (UUID) of the Custom Field you want to set.
If you want to reference a task by its Custom Task ID, this value must be true.
Only used when the custom_task_ids parameter is set to true. For example: custom_task_ids=true&team_id=123.
The value must be a string with a valid URL.