Conciseness

The body is ~720 lines with essentially no prose padding, but much of it restates the C++ Core Guidelines — rule-summary tables (P.*, F.*, C.*...), full Rule of Five and RAII implementations — that Claude already knows well. Anchor 3 fits: mostly efficient per-section, but the full Buffer/FileHandle listings and rule inventories could be tightened or trimmed since Claude can generate canonical RAII code itself.

Actionability

Concrete, executable code throughout: complete DO/DON'T examples ("explicit Buffer(std::size_t size)...", "std::scoped_lock lock(from.mutex_, to.mutex_)", "cv_.wait(lock, [this] { return !queue_.empty(); })") plus explicit anti-pattern lists per section. Code is copy-paste ready and covers the common cases, matching the anchor-5 example.

Workflow Clarity

Not a step-sequence skill but a reference standard; its structure (When to Use / NOT to Use → Cross-Cutting Principles → per-area rules with DO/DON'T → "Quick Reference Checklist: Before marking C++ work complete") provides a clear usage sequence with a terminal checklist checkpoint. Not 5 because there are no intermediate validation/feedback checkpoints (e.g., how to check compliance incrementally); not 3 because the closing checklist is an explicit verification step and the organization is coherent.

Progressive Disclosure

No bundle files exist (no references/, scripts/, or assets/), so all ~720 lines are inlined in SKILL.md. Section headers are clear, but the deep-dive material — full Rule of Five and RAII implementations, per-section rule tables — clearly belongs in one-level-deep reference files with a lean overview, matching anchor 3 ("content that should be separate is inline"). Not 4 because there is no reference-file split or navigation to slower-loading detail at all.

Specificity

Quotes: "C++ coding standards based on the C++ Core Guidelines (isocpp.github.io)" names a concrete, authoritative source, and "writing, reviewing, or refactoring C++ code" lists three specific user tasks. Not 5 because "enforce modern, safe, and idiomatic practices" leans on generic adjectives rather than concrete capabilities; not 3 because multiple concrete actions are named beyond a bare domain label.

Completeness

Quotes: what — "C++ coding standards based on the C++ Core Guidelines (isocpp.github.io)"; when — "Use when writing, reviewing, or refactoring C++ code". Both are explicit and the when clause carries concrete trigger phrases, matching the anchor-5 example pattern almost exactly. Not 4 because the 'when' is already as explicit and specific as the rubric's best example.

Trigger Term Quality

Quotes: "C++", "writing, reviewing, or refactoring C++ code" — natural phrases users would say, plus the recognizable "C++ Core Guidelines" and "isocpp.github.io". Not 5 because it lacks common variations like ".cpp", "C++17/20", "style guide", or "lint" that users might use; not 3 because coverage of the core natural terms is good, not partial.

Distinctiveness Conflict Risk

Quotes: "C++ coding standards" and "refactoring C++ code" — a clear language-scoped niche with distinct triggers. Not 5 because "reviewing... C++ code" and "refactoring" overlap with generic code-review/refactoring skills, a minor conflict risk with closely related skills; not 3 because the explicit C++ restriction keeps it far more distinct than a broad domain claim.