The body is lean and directive — "You improve runtime, size, or memory without changing behaviour. Speculative micro-optimisations are not welcome." — with no padding and no explanation of concepts Claude already knows.

Concrete named techniques such as "prefer `requestIdleCallback`," "use `DocumentFragment`, prefer `transform` over `top/left`," and "WebP over PNG/JPG" give specific actionable guidance; absence of full code blocks is acceptable for an instruction-only skill.

A sequence exists (Before changing anything → ordered Common wins → Don't), but there is no validation/checkpoint step to confirm behaviour is unchanged or to measure the improvement, which the "without changing behaviour" premise demands.

The skill is under 50 lines, single-purpose, and organized into clear sections with no need for external references, fitting the simple-skill allowance for a top progressive-disclosure score.

"Make existing code faster, smaller, or more efficient" names three concrete optimization outcomes, matching the anchor that lists multiple specific actions rather than vague language like "Helps with code."

The description states what the skill does but contains no "Use when..." trigger clause; the when-guidance lives in a separate `when_to_use` field, so the description alone lacks explicit trigger guidance and is capped at 2.

The terms "faster," "smaller," and "more efficient" are natural, but the description misses common variations users actually say such as "slow," "performance," "optimize," or "latency."

The optimization niche is reasonably clear, but without explicit triggers in the description it could still overlap with general refactor or code-quality skills.