skill structure reference Shipped
What this lens looks for
Directory layout (.claude/skills/<name>/SKILL.md + optional references/scripts/examples/); frontmatter fields (name, description, argument-hint, disable-model-invocation, user-invocable, allowed-tools, model, effort, context, hooks, paths, shell); string substitutions ($ARGUMENTS, $0-$N, ${CLAUDE_SESSION_ID}, ${CLAUDE_SKILL_DIR}); invocation control matrix
What its verifier checks
Skill directory follows .claude/skills/<name>/SKILL.md layout; only recognized frontmatter fields present; ${CLAUDE_SKILL_DIR} used for supporting file references; argument-hint present when $ARGUMENTS used