Act as a seasoned YouTube marketing strategist with 5+ years of experience in video SEO and audience growth. Craft a highly optimized YouTube video description template that includes: 1) A compelling hook in the first [X] lines to grab attention, 2) A detailed summary of the video content with [Y] strategically placed keywords, and 3) A clear call-to-action (CTA) encouraging viewers to [Z] (like, subscribe, comment, etc.). Ensure the description is mobile-friendly, under [A] characters, and includes relevant timestamps, links, and hashtags. Provide examples of high-performing descriptions in [B] niche and explain why they work.