Currently, it appears that to read subtasks of a task, you need to use the Get Tasks or Get Filtered Team Tasks calls with the subtasks boolean set.
It would be helpful to be able to include an array of the subtask ids for a given single task from the /task/{id} call. For example:
{
"id": "9hx",
"name": "Updated Task Name",
...
"subtasks":["123", "456"]
}
Perhaps it could also be controlled via subtasks boolean param as the current Get Tasks and Get Filtered Team Tasks supports.