Copy this shape, then replace every line
Line one: the promise, in the same words as the title. Line two: who it is for, or the result they will see. Then a blank line. Then chapters if the video is long enough to skip, with the first stamp at 0:00. Then one link to the playlist or the next video. Then three to five hashtags that name the topic.
The description generator drafts that opening from the topic you type. The description guide explains why the first lines matter.
Chapters only count when they start at zero
A list of times that begins at 1:30 is not the pattern YouTube uses for chapters. Start at 0:00 and add at least two more stamps. Name each chapter the way you would say it out loud.
Do not stuff keywords under the chapters
A paragraph of repeated phrases does not make the topic clearer than the title you already wrote. Tags, in the tag box rather than the description, are a minor signal for misspellings. Keep the combined tag list under YouTube's 500-character limit.
Check the uploads that skip the template
The mini-audit flags descriptions under 100 characters and long videos without chapters. Run it, fix those videos, and keep the template for the next upload. Paid plans can store the rewritten description with the audit. Unlimited can apply a previewed description to YouTube. It does not apply one you have not confirmed.