https://developers.strava.com/docs/reference/#api-models-SummarySegment

starred, hazardous, elevation_profile and elevation_profiles are missing in the documentation

athlete_pr_effort, athlete_segment_stats are only specified in the documentation. Which is a shame. Without fetching each and every segment details for an activities segment (which of course would be madness), I cannot figure out a way to show the user which segments they have completed before and which they are completing for the first time.

See fields of an entry in segment_efforts in a detailed activity:

{
    "id": 4803742,
    "resource_state": 2,
    "name": "Montvernier-Col du Chaussy",
    "activity_type": "Ride",
    "distance": 13785.6,
    "average_grade": 7.7,
    "maximum_grade": 600,
    "elevation_high": 1533.4,
    "elevation_low": 522,
    "start_latlng": [
        45.31567,
        6.338058
    ],
    "end_latlng": [
        45.343899,
        6.356372
    ],
    "elevation_profile": null,
    "elevation_profiles": null,
    "climb_category": 5,
    "city": "Pontamafrey-Montpascal",
    "state": "Rhône-Alpes",
    "country": "France",
    "private": false,
    "hazardous": false,
    "starred": false
}