Youtube already offers AI transcriptions on their site. As another commenter points out, you grab them with yt-dlp.
And unlike how your tool will be supported in the future, thousands of users make sure yt-dlp keeps working as google keep changing the site (currently 1459 contributors).
if you used this in earnest sufficiently, you'd know yt default transcripts are not good enough because youtube often (ok say 5% of time) fails to transcribe videos particularly livestreams and shortly after release.
the volunteer open source effort behind youtube-dl and its forks/descendants are so impressive in large part because of how many features they provide and thus have to maintain:
https://github.com/yt-dlp/yt-dlp#usage-and-options
this tool won't provide the list of available thumbnails or settings for HTTP buffer size, but I think that's a pretty reasonable tradeoff.
And unlike how your tool will be supported in the future, thousands of users make sure yt-dlp keeps working as google keep changing the site (currently 1459 contributors).