Conciseness

The body is dense with domain-specific, non-obvious material (DAL/ASIL-to-criterion mapping, LLVM_PROFILE_FILE patterns, semihosting specs, __gcov_reset()) and avoids explaining basics Claude already knows. Minor over-explanation could be trimmed: the verbatim GCC quotation about --coverage is long, and the 'produce lcov.info, render HTML, gate the PR' advice is repeated nearly verbatim in 'How to use' and 'Coverage report formats'. This is the level-4 anchor ('efficient; minor instances of over-explanation'), not level 5 where every token earns its place.

Actionability

Guidance is fully executable and copy-paste ready: complete compile/run/report command blocks for both toolchains (arm-none-eabi-gcc --coverage -O0, clang -fprofile-instr-generate -fcoverage-mapping -fcoverage-mcdc, llvm-profdata merge, llvm-cov show/report/export, lcov/genhtml), plus concrete specifics like --specs=rdimon.specs, LLVM_PROFILE_FILE patterns, and __gcov_reset(). The worked example covers the common host-build case end to end, matching the level-5 anchor.

Workflow Clarity

The 'How to use' section gives a clear 5-step decision sequence (criterion → toolchain → instrument at -O0 → where to run → artefact/gate), each step pointing to the supporting section, and the worked example walks one module end to end. Validation checkpoints are present but implicit (scan for ##### lines, gcov-tool overlap for saturated counts) rather than explicit validate-before-proceeding steps, so it sits at level 4 rather than level 5.

Progressive Disclosure

SKILL.md is a well-organized overview, and both inline references ([references/gcov-flag-reference.md], [references/safety-standards-and-formats.md]) point to real files that exist in the bundle and hold exactly the deep material (flag table, standards/format matrices) kept out of the overview. References are one level deep — the reference files link back to the SKILL, not onward to further files — and a References section lists them for discovery, matching the level-5 anchor.

Specificity

The description lists multiple concrete actions with named tools and criteria: "deciding what code coverage level embedded C/C++ needs (statement, branch, MC/DC)", "wiring gcov or llvm-cov into the build", "host vs QEMU instrumentation", "MISRA-C and DO-178C expectations by safety level", and "report formats". This comprehensively covers the skill's capabilities, matching the level-5 anchor rather than level 4, which only expects 'several specific actions; minor gaps'.

Completeness

Both 'what' (criterion selection, toolchain wiring, standards expectations, report formats) and 'when' (explicit "Use when deciding... and wiring gcov or llvm-cov into the build" trigger clause with concrete trigger phrases) are clearly and explicitly stated. It matches the level-5 anchor example structure exactly; level 4 would require the 'when' to be less explicit than it is here.

Trigger Term Quality

Good keyword coverage of natural terms users would say: "code coverage", "gcov", "llvm-cov", "MC/DC", "embedded C/C++", "MISRA-C", "DO-178C", "QEMU". A few natural terms are missing, though — "lcov", "ISO 26262 / ASIL" (which the body covers), and "clang" — which fits the level-4 anchor ('good keyword coverage; a few natural terms missing') rather than the comprehensive level-5 anchor.

Distinctiveness Conflict Risk

The description carves out a clear niche — coverage-criterion strategy and instrumentation for embedded C/C++ with gcov/llvm-cov under safety standards — with distinct trigger terms that would not fire for generic test-framework or build skills. Minimal conflict risk, matching the level-5 anchor.