To update YouTube video descriptions and tags using Zapier, you’ll want to set up a Zap that connects your trigger app with YouTube, targeting video updates. Unfortunately, Zapier's direct options for updating existing YouTube videos are limited, often due to restrictions within YouTube's API, which can sometimes lead to the "400 Bad Request" error you're experiencing. One workaround is to use the "YouTube API Request" feature in Zapier’s Webhooks by Zap action. With this, you can manually configure an API request to update video details, including the description and tags. To do this, you'll need to enable the YouTube Data API, set up authentication, and specify the video ID, description, and tags within the request body. This approach requires some technical setup but gives you the control to update your video details dynamically.