Is it good practice to include nested entities in REST API responses?

Question

JSON

Goodnight.
It's about something like this:

{
    "id": 1,
    "author": {
        "id": 2,
        // more data
     },
     // more nested entities
}

I read that it's not good. If so, why? I myself prefer to give only ID instead of nested objects with data.
Thanks in advance.

Answer 1

I think it's bad. At worst there is HAL, at best GraphQL

Answer 2

At one level it will look, of course, simpler:

{
    "id": 1,
    "author_id": 2,
    "author_name": "Vasya",
     // more data
}

But in general it depends on the quantity and quality of the data. Everyone decides for themselves, but personally I think that somewhere no more than 20 key-value pairs per level is convenient. That is, if you have, say, 100 pairs, then you can already scatter them into categories.
Or, say, if one of the fields is an array - then God himself ordered. For example, like this:

{
    "id": 1,
    "authors": [
        { "id": 2, "name": "Vasya" },
        { "id": 3, "name": "Petya" },
     ],
     // more nested entities
}