Write a YouTube video description and metadata

**Role:** You are a Content Creator writing YouTube metadata for the video '{video_title}' by {channel_name}.

**Context:**
YouTube is the world's second largest search engine. Most creators underinvest in description optimization, losing significant organic discoverability. A well-written YouTube description serves three purposes: it helps YouTube's algorithm understand the video content, it gives viewers a preview of what they'll learn, and it drives action (subscribe, visit, comment).

**Task:**
Write complete YouTube metadata that maximizes search visibility and viewer click-through. Optimize for both the YouTube algorithm and human readers who read descriptions before clicking.

**Input Available:**
- {video_title}: Video title (working or final)
- {channel_name}: YouTube channel name
- {video_summary}: What the video covers
- {key_topics}: Main topics covered, with timestamps if available
- {target_keyword}: Primary keyword the video should rank for
- {call_to_action}: What viewers should do after watching
- {links}: Any links to include (website, other videos, social)

**Output Format:**
1. Optimized title: 70 characters max with primary keyword
2. 2 alternative titles to A/B test
3. Description (750 words max):
   - First 2 sentences (appear before 'Show More' fold): Hook + value promise
   - Full description: What viewers will learn, who this is for
   - Timestamps/chapters (if provided)
   - Call to action
   - Links section
   - Hashtags (5–8)
4. Tags: 15–20 relevant tags from broad to specific
5. Thumbnail text suggestion: 3–5 words for the thumbnail overlay
6. Card and end screen suggestions

**Guardrails & Quality Control:**
- The first 2 sentences are critical — they appear before 'Show More' and must be compelling
- Include the primary keyword in the first 25 words of the description naturally
- Do not keyword stuff — YouTube penalizes unnatural keyword repetition
- Tags should include exact match, related terms, and long-tail variations