Why does /v2/athlete return no data, or no age or sex for some providers?

/v2/athlete sends its result to your destination unless you set to_webhook=false, and the profile fields it returns depend on the provider.

/v2/athlete delivers to your destination by default, so the immediate response holds no profile. Add to_webhook=false to get it inline. It doesn't need a start_date.

The fields you get depend on what each provider shares:

Provider	Profile fields returned
Fitbit	First and last name, age, date of birth, gender, country, state, bio, date joined
Oura	Age, sex, email
Wahoo	First and last name, gender, email, date joined, and age and date of birth when set
Zepp	Gender, date of birth (year and month)
WHOOP	First and last name, email
Garmin	Nothing. The profile comes back empty

The athlete object has no height or weight. Read those from /v2/body.

See the athlete data model and why GET requests return no data array.