Conciseness

The body is dense and expert-level throughout — it assumes competence (never explains what Asio or coroutines are), and time-sensitive version numbers are consolidated into a dedicated 'version floors' table rather than scattered prose. Minor duplication keeps it below anchor 5: the CI-verified claim appears in both the Overview and Worked examples sections, and the Overview sentence 'Use this skill whenever async C++ networking code is being written or reviewed' repeats the frontmatter description.

Actionability

Fully executable guidance throughout: concrete detection commands ('dpkg -l libboost-dev', 'brew info boost'), a version→style→file decision table, exact flags ('$<$<CXX_COMPILER_ID:GNU>:-fcoroutines>', 'BOOST_ERROR_CODE_HEADER_ONLY'), a copy-paste-ready namespace shim code block, and links to three CI-verified implementations. This matches anchor 5 ('copy-paste ready code or commands; specific examples cover the common cases').

Workflow Clarity

A clearly sequenced multi-step process ('Step 1: pick the style' → 'Step 2: version floors' → 'Step 3: the rules') with an explicit validation checkpoint ('It compiles. Build it — most of the mistakes above are compile-time'), a terminal 'Before you call it done' checklist mapping back to each rule, and a Mistake→Fix anti-patterns table for error recovery. This matches anchor 5 (clear sequence, explicit validation, feedback paths, checklist).

Progressive Disclosure

The body is a genuine overview/router with only the highest-value rules inline; all five referenced files (coroutines.md, pre-cpp20.md, classic-boost.md, ssl.md, build.md) exist in references/, are exactly one level deep, and are clearly signaled via the decision table's 'Read' column and per-topic pointers. This matches anchor 5 ('clear overview with well-signaled one-level-deep references; content appropriately split; easy navigation').

Specificity

The description names the domain ('asynchronous C++ networking code with Boost.Asio or standalone Asio') and concrete actions ('writing or reviewing') with a near-comprehensive scope enumeration ('TCP/UDP servers and clients, SSL/TLS, timers, strands, io_context, co_spawn, awaitable, async_read/async_write'), but it lists only two action verbs rather than multiple distinct deliverable actions, so it matches anchor 4 ('several specific actions; minor gaps') rather than anchor 5.

Completeness

An explicit 'Use when...' trigger is present and the 'what' is embedded ('writing or reviewing asynchronous C++ networking code... with [these features]'), but what and when are merged into a single clause and the skill's distinct deliverables are not enumerated separately. It sits between anchor 4 ('both what and when; when could be more explicit') and anchor 5, and is noticeably above the midpoint rather than a clear anchor-5 match.

Trigger Term Quality

It covers the natural vocabulary a user doing Asio work would actually say — 'io_context', 'co_spawn', 'awaitable', 'async_read/async_write', 'asio::spawn', 'yield_context', 'strands', 'completion-handler callbacks' — including both library synonyms (Boost.Asio and standalone Asio). This matches anchor 5's comprehensive coverage including synonyms; anchor 4 ('a few natural terms missing') understates it.

Distinctiveness Conflict Risk

The niche is unmistakable — Boost.Asio/standalone Asio with API-level triggers like 'co_spawn', 'awaitable', and 'yield_context' — so it would not fire for any other skill. This matches anchor 5 ('clear niche with distinct triggers; minimal conflict risk'). Voice is third-person, so no specificity penalty applies.