Conciseness

The ~25-line body is lean and assumes Claude's competence throughout — no explanation of what design patterns are, why composition beats inheritance, or what a regression test is; every line is either a rule or a pointer ("Prefer composition over deep inheritance", "extend it, never fork it"). It matches anchor 5 ('lean and efficient; every token earns its place') and clearly not anchor 4, which reserves room for over-explanation that is simply absent here.

Actionability

For an instruction-only skill the guidance is concrete: it names the patterns to follow ("BaseIntegrator, CommandLogger, AuthResolver"), enumerates the exact canonical owners to route through, and specifies a verifiable enforcement step — "a regression test plus a static check in `scripts/lint-architecture-boundaries.sh`". This is mostly-executable per anchor 4; it stops short of 5 because the referenced script and the full rule file are not present in the skill bundle, so the guardrail command cannot actually be run or copied from what is shipped.

Workflow Clarity

No sequence is given for an architectural change (when to inspect existing patterns, when to introduce a base class, when to add the guardrail); the guidance is a rules list, and the one checkpoint that does exist — the dual guardrail of regression test plus lint check — is stated as a rule, not woven into an ordered workflow. That matches anchor 3 ('sequence present but checkpoints missing or implicit' — here the checkpoints are isolated and the sequence implicit); it cannot score 4 because the simple-skill exception does not apply: this skill explicitly targets complex 3+ file refactors, a multi-step process, and the ordering of analysis → design → guardrail is left implicit.

Progressive Disclosure

The body is a clean overview with clear sections ('When to activate', 'Key rules'), and the longest rule — canonical ownership — correctly inlines only a summary while pointing to the full rule at `.apm/instructions/architecture.instructions.md`, exactly the one-level-deep pattern anchor 4 describes. It does not reach 5 because the bundle contains no references/, scripts/, or assets/ directories, so the three referenced paths (`scripts/lint-architecture-boundaries.sh`, `.apm/instructions/architecture.instructions.md`, `../../agents/python-architect.agent.md`) are unverifiable or outside the skill, leaving minor organization gaps.

Specificity

Phrases like "creating new modules, refactoring class hierarchies, introducing design patterns, or making changes spanning 3+ files" list several concrete, domain-specific actions, but they are all trigger conditions — the description never states what the skill actually does (provide architectural rules/guidance), so coverage of capabilities is one-sided. This sits between anchor 3 (1-2 concrete actions, not comprehensive on the capability side) and anchor 4 (several specific actions), with the missing 'what' keeping it at 3 rather than 4.

Completeness

The 'when' is fully explicit ("Activate when creating new modules, refactoring class hierarchies, introducing design patterns, or making changes spanning 3+ files in the APM CLI codebase"), but the 'what' is entirely absent — the description is a pure trigger clause with no statement of capability, mirroring anchor 3's incompleteness in reverse. It is above anchor 2 ('only when present') because that anchor's example is vague, whereas here the 'when' is detailed and concrete; it cannot reach 4 because anchor 4 requires both what AND when.

Trigger Term Quality

"creating new modules", "refactoring class hierarchies", "introducing design patterns", and "changes spanning 3+ files" are phrases a user would plausibly say verbatim when needing this skill, matching anchor 4's 'good keyword coverage; a few natural terms missing'. It falls short of 5 because natural synonyms users might say — e.g. 'base class', 'restructure', 'abstraction', or pattern names like 'Strategy/Observer' — appear only in the body, not in the description.

Distinctiveness Conflict Risk

The scope to "the APM CLI codebase" and architectural vocabulary ("class hierarchies", "design patterns") give it a clear niche, but the very broad trigger "making changes spanning 3+ files" would fire on many multi-file changes that are not architectural — e.g. renames, bulk edits, or test additions — creating real overlap risk with general refactoring or code-review skills. This matches anchor 3 ('somewhat specific but could still overlap with similar skills'); not 4 because the 3+ files trigger is a common situation rather than a distinct architectural signal.