Is it acceptable to only include relationship data on certain endpoints?

Hi there.

I hope the topic is self-explanatory.

Basically, in my API I have two resource types: albums and tracks.

There are two endpoints, one for paginating all albums in the system (/albums), and one for fetching a single album (/albums/$ALBUM_ID).

This is an example response for paginating albums:

{
  "data": [
    "type": "albums",
    "id": "1",
    "attributes": {
      "name": "Album 1"
    },
    "relationships": {
      "tracks": {
        "links": {
          "related": "/albums/1/tracks"
        }
      }
    }
  ]
}

And this is an example response for viewing a specific album:

{
  "data": {
    "type": "albums",
    "id": "1",
    "attributes": {
      "name": "Album 1"
    },
    "relationships": {
      "tracks": {
        "data": [
          {"type": "tracks", "id": 1},
          {"type": "tracks", "id": 2},
          {"type": "tracks", "id": 3}
        ],
        "links": {
          "related": "/albums/1/tracks"
        }
      }
    }
}

Is this considered valid according to the spec? Specifically with regards to only including the actual relationship data when viewing a single album. When paginating albums, the relationship data is not included.