Conciseness

The body is short with no over-explanation of concepts Claude already knows, but it is not tight: the intro sentence echoes the frontmatter description nearly verbatim, the 'Use/Do not use' lists duplicate the description's triggers, and the reference to `resources/implementation-playbook.md` is stated twice (in Instructions and again in Resources). This matches 'mostly efficient but could be tightened' rather than a 4, where only minor trimming would be needed — three separate redundancies are present.

Actionability

The four steps are high-level hints — 'Clarify domain boundaries, constraints, and scalability targets', 'Select an architecture pattern that fits the domain complexity', 'Define module boundaries, interfaces, and dependency rules' — with no decision criteria for choosing among Clean/Hexagonal/DDD, no example boundary or dependency-rule structures, and no concrete migration steps. This matches the 'minimal concrete guidance; high-level hints but missing the specific steps to execute' anchor; it is not a 3 because even the details it promises ('detailed patterns, checklists, and templates') live in a referenced file that does not exist in the bundle, leaving no concrete material at all.

Workflow Clarity

The four numbered steps form a coherent sequence (clarify → select → define → provide migration/validation), matching 'steps listed but validation gaps; checkpoints missing or implicit'. Validation appears only as a deliverable to 'provide', never as an actual checkpoint in the workflow. Not a 2 because, unlike the 2-anchor, the sequence is present and each step maps to a distinct, sensibly ordered phase; not a 4 because the steps themselves are vaguely defined and no verification checkpoint is explicit.

Progressive Disclosure

Scored against the actual bundle structure as the guidelines direct: there are no `references/`, `scripts/`, `assets/`, or `resources/` files, so `resources/implementation-playbook.md` — to which the skill defers all detailed patterns, checklists, and templates — does not exist. The on-paper structure (clear sections, one clearly signaled one-level reference) would suggest a 4, but the bundle delivers nothing beyond the overview, so the skill is neither self-contained nor appropriately split; this lands noticeably below the midpoint. Not a 1 because the body itself is navigable with clear headers and the reference is signaled, not buried.

Specificity

The description names the domain and three concrete patterns ('Clean Architecture, Hexagonal Architecture, and Domain-Driven Design') plus actions ('Implement', 'architecting', 'refactoring'), matching the 'several specific actions with minor gaps' anchor. It falls short of a 5 because 'Implement' is the only capability verb — it does not state what it does with those patterns (e.g., define module boundaries, produce migration plans), leaving minor coverage gaps.

Completeness

Both parts are explicit: the 'what' is 'Implement proven backend architecture patterns including Clean Architecture, Hexagonal Architecture, and Domain-Driven Design' and the 'when' is 'Use when architecting complex backend systems or refactoring existing applications for better maintainability' — a concrete trigger clause that mirrors the 5-anchor example's structure. It is not a 4 because the 'when' clause is already explicit and specific rather than merely present.

Trigger Term Quality

Good natural-keyword coverage: 'backend architecture', 'Clean Architecture', 'Hexagonal Architecture', 'Domain-Driven Design', 'architecting complex backend systems', 'refactoring', 'maintainability' — phrases users would actually say. Not a 5 because common synonyms and variations are missing ('onion architecture', 'ports and adapters', 'DDD', 'domain modeling').

Distinctiveness Conflict Risk

The Clean/Hexagonal/DDD niche is clear and mostly distinct from generic coding skills, matching the 'mostly distinct; minor overlap risk' anchor. Not a 5 because 'refactoring existing applications for better maintainability' could overlap with a general refactoring or code-quality skill's triggers.