The body is lean — a compact quick-start, an abstractions table, a small ASCII model, and terse do's/don'ts — with every section earning its place and no padding with concepts Claude already knows.

It provides an executable Cargo.toml and a complete `#[tokio::main]` Rust example plus concrete directives (use `tokio::select!`, `JoinSet`, `CancellationToken`; don't `std::thread::sleep`, don't hold locks across awaits), copy-paste ready.

This is a single-purpose pattern-reference skill with no destructive or batch operations requiring validation; per the simple-skills note, the unambiguous, well-organized guidance scores 3, and the one-level navigation tier is clearly signaled.

The body is a concise overview and detailed patterns are split into the verified one-level-deep `references/details.md`, explicitly signaled with when to read it ("when the navigation tier above is insufficient").

Names multiple concrete capabilities — "Tokio, async traits, error handling, and concurrent patterns" — which read as distinct, specific domains rather than vague abstraction, matching the multiple-specific-actions anchor.

It explicitly answers what ("Master Rust async programming with...") and when ("Use when building async Rust applications, implementing concurrent systems, or debugging async code") with an explicit trigger clause.

The "Use when..." clause surfaces natural phrases users would actually say — "building async Rust applications", "implementing concurrent systems", "debugging async code" — giving good coverage of natural terms.

The async Rust/Tokio niche is sharply defined with distinct triggers, making it unlikely to fire for unrelated skills.