Conciseness

The body is lean and imperative — "Trace the code path from the symptom back to potential causes", "Minimal diff: Fewest files touched, fewest lines changed" — with no explanations of concepts Claude already knows. It is not 5 because of repeated material: 'Recurring bugs in the same files are an architectural smell' appears in both Phase 1 and Phase 2, the '>5 files' flag appears in Phase 4 and again in Important Rules, and the 3-strike rule is stated twice.

Actionability

For an instruction-only skill, guidance is fully concrete and executable: a copy-paste command (`git log --oneline -20 -- <affected-files>`), exact output formats ("Root cause hypothesis: ..."), a verbatim user-facing 3-strike message, defined statuses (DONE | DONE_WITH_CONCERNS | BLOCKED), and a structured DEBUG REPORT template. It is not 4 because no key execution detail is missing.

Workflow Clarity

Five clearly sequenced phases with explicit validation checkpoints and feedback loops: hypothesis must be confirmed with evidence before any fix, a wrong hypothesis loops back to Phase 1, the 3-strike rule stops runaway guessing, the regression test must fail without the fix and pass with it, and Phase 5 mandates fresh reproduction. This matches the top anchor (explicit validation steps, feedback loops, error-recovery paths).

Progressive Disclosure

No bundle files exist (references/, scripts/, assets/ are absent), and the ~130-line body is cleanly sectioned into distinct phases, so nothing is misfiled or buried. It is not 5 because the skill exceeds 50 lines and the Phase 2 pattern catalog and the DEBUG REPORT format are self-contained chunks that could live in one-level-deep reference files, keeping SKILL.md a tighter overview.

Specificity

The description names the debugging/root-cause domain via phrases like "debug, fix a bug, investigate an error, or do root cause analysis", but describes no concrete capabilities of the skill itself — what it actually does (systematic investigation phases, hypothesis testing, regression-test requirements, debug reports) is entirely absent. It matches 'names the domain but actions are minimal or generic' rather than level 3, which requires 1-2 concrete actions to be stated.

Completeness

Only the 'when' is present — the entire description is a 'Use when...' trigger clause with no statement of what the skill does. This matches anchor 2 ('only when is present without what') exactly. It is not 1 because the 'when' is concrete and multi-faceted, and not 3 because anchor 3 requires a clear 'what', which is missing entirely.

Trigger Term Quality

Trigger coverage is comprehensive and natural: "debug", "fix a bug", "investigate an error", "root cause analysis", "stack traces", "unexpected behavior", and "something stopped working" — these are exactly the phrases users say, including synonyms and both user-report and direct-request framings. It is not level 4 because no natural terms are missing.

Distinctiveness Conflict Risk

Phrases like "root cause analysis" and "stack traces" carve out a distinct debugging niche with low conflict risk against most skills. It is not 5 because broad triggers like "debug" and "fix a bug" could overlap with general code-review, testing, or verification skills.