TMDB only uses JavaScript Object Notation(JSON) as the only text-based format for storing and displaying data.
if you are adding any body response to any of the endpoints, the format is like this:
Validating Request token with login details
     curl --request POST \
          --url https://api.themoviedb.org/3/authentication/token/validate_with_login \
          --header 'Authorization: Bearer {ACCESS_TOKEN}' \
          --header 'accept: application/json' \
          --header 'content-type: application/json' \
          --data '
     {
     "username": "johnny_appleseed",
     "password": "test123",
     "request_token": "1531f1a558c8357ce8990cf887ff196e8f5402ec"
     }
If you are using a JavaScript library and need to make requests from another public domain, you can use the callback paramater which will encapsulate the JSON response in a JavaScript function for you.
Example JSONP Request
curl --request GET \
     --url 'https://api.themoviedb.org/3/search/movie?query=Batman&callback=test' \
     --header 'Authorization: Bearer ACCESS_TOKEN' \
     --header 'accept: application/json'