Include child entries of a given parent Id

I have contents like below:


  1. BookLocations[] (Type of Location)


  1. US - Id: 123
    1. New York - Id: 234
    2. Seattle - Id: 567

When I search like below:{space_id}/environments/{environment_id}/entries?access_token={access_token}

This does not fetch child entries which are linked to “New York” or “Seattle”.
Is there any way to include children as well?

Did you try[in]=123?

It requires .fields to be in the path.

Does the field kind of helpfully