How to get Youtube video transcript with YT API

I relate to this solution, which doesn't work for me as expected: https://stackoverflow.com/a/35555773/1992004

Example URL: https://www.youtube.com/watch?v=WECQWfbrDRA

Accessing YT API with request, recommended in the cited solution, https://www.googleapis.com/youtube/v3/captions?videoId=WECQWfbrDRA&part=snippet&key=MYKEY I get an answer without transcript:

{"kind": "youtube#captionListResponse","etag": "_Q7mhkZOxmnB-OUYZtFh3NfoQTA","items": [    {"kind": "youtube#caption","etag": "inJmvEc9uoy20P6cTHGDrBw7Ucw","id": "AUieDaY04UW8eDU0F_kn4QlGzc7lJriXOz42Nqc20cmkmQN759U","snippet": {"videoId": "WECQWfbrDRA","lastUpdated": "2023-12-12T18:47:57.150575Z","trackKind": "asr","language": "de","name": "","audioTrackType": "unknown","isCC": false,"isLarge": false,"isEasyReader": false,"isDraft": false,"isAutoSynced": false,"status": "serving"      }    }  ]}

But accessing example video with a service like this, transcript exists.

Am I doing something wrong?

PS: It seems to me, 'caption' in terms of YT API is something other as transcript of the video.