The body is dense and assumes Claude's competence — no elementary explanations, no fluff; every line ('Minimize concepts, states, interfaces, irreversible decisions...', 'A verdict records the decision gate and never expands authorization') earns its place, matching the lean-and-efficient anchor.

Concrete executable guidance throughout: a named decision-gate sequence, a consumer-question table, an ordered solution-preference list, evidence labels ('VERIFIED', 'INFERENCE', 'UNKNOWN'), and explicit verdicts ('STOP', 'REDUCE', 'REVISE', 'PROCEED', 'NEEDS_EVIDENCE') that map conditions to actions, matching the fully-actionable anchor for an instruction-only skill.

The six numbered gates form a clear sequence with explicit validation checkpoints — 'Reproduce the baseline first', 'Map each important result claim to observed evidence', 'Verify negative boundaries and failure behavior' — plus feedback loops (re-validate, NEEDS_EVIDENCE) satisfying the clear-sequence-with-validation anchor.

No bundle files exist, so the single SKILL.md is appropriately self-contained; content is well-organized under clear section headings (Preserve the Task Boundary, Apply the Decision Gates, Use Explicit Verdicts, Keep the Output Proportional) with no nested-reference indirection, matching the well-organized-structure allowance for skills needing no external references.

Lists multiple concrete actions — 'assessing RFCs, issues, designs, features, refactors, migrations, dependency changes' plus 'proposed fields, events, APIs, modules, and services' — matching the 'lists multiple specific concrete actions' anchor.

Explicitly answers both 'what' ('Evaluate and carry out non-trivial software-system changes from first principles') and 'when' via the 'Use when assessing...' clause, satisfying the explicit-trigger anchor and avoiding the cap at 2.

Natural user terms are well covered: 'RFCs, issues, designs, features, refactors, migrations, dependency changes' are the vocabulary users actually invoke this skill with, matching the 'good coverage of natural terms' anchor.

Niche is clearly delimited — 'whose need, consumers, system fit, validation, or rollback require scrutiny' and the exclusion 'Do not use for mechanical edits, source-code explanation, or a dedicated review of an already-complete diff' sharply separates it from overlapping skills.