If you are building a RAG or agent pipeline over video, the transcript is the payload. Titles and descriptions are thin; a 40-minute talk is thousands of tokens of dense, quotable prose. The good news is that YouTube already exposes that prose as captions. The bad news is that pulling captions for videos you do not own, at batch scale, is where most naive pipelines fall over. This post walks through the source-of-truth question, the official-API dead end, a working Python path into a vector stor...