docs: align skill contribution guidance

CONTRIBUTING.md

@@ -7,7 +7,7 @@ Thanks for your interest in contributing! This project is a collection of produc
 1. Create a directory under `skills/` with a kebab-case name
 2. Add a `SKILL.md` following the format in [docs/skill-anatomy.md](docs/skill-anatomy.md)
 3. Include YAML frontmatter with `name` and `description` fields
-4. Ensure the `description` starts with "Use when" and describes triggering conditions
+4. Ensure the `description` briefly says what the skill does, then includes clear "Use when" trigger conditions
 
 ### Skill Quality Bar
 
@@ -20,7 +20,12 @@ Skills should be:
 
 ### Structure
 
-Every skill should include these sections:
+Every new skill must have:
+
+- `SKILL.md` in the skill directory
+- YAML frontmatter with valid `name` and `description`
+
+New skills should generally follow the standard anatomy:
 
 - **Overview** — What this skill does and why it matters
 - **When to Use** — Triggering conditions