Lists multiple specific concrete actions: designing module boundaries, APIs, layers, abstractions, services, repositories, adapters; creating deep modules, hiding implementation knowledge, avoiding leakage and pass-through APIs, comparing alternative designs, documenting interfaces, critiquing existing architecture.

Clearly answers both 'what' (designing module boundaries, creating deep modules, hiding implementation knowledge, comparing alternative designs, documenting interfaces, critiquing architecture) and 'when' ('before implementing or refactoring software when the task requires designing module boundaries, APIs, layers, abstractions, services, repositories, adapters, or architecture').

Includes strong natural keywords users would say: 'module boundaries', 'APIs', 'layers', 'abstractions', 'services', 'repositories', 'adapters', 'architecture', 'refactoring', 'designing'. These cover a wide range of terms a developer would naturally use when needing architecture guidance.

While it targets software architecture specifically, terms like 'refactoring', 'APIs', 'services', and 'coding' could overlap with general coding or refactoring skills. The focus on design-before-coding and architecture critique helps distinguish it, but there's moderate overlap risk with broader development skills.

The content is mostly efficient and avoids explaining basic concepts Claude already knows, but some sections are somewhat verbose—particularly the Decision Rules Summary which restates principles that overlap with the workflow and design gates sections. The design brief template and mandatory gates have significant overlap.

The skill provides highly concrete, actionable guidance: a specific design brief template, a numbered workflow with clear steps, explicit decision rules, mandatory design gates with specific questions, and clear instructions for when to stop and revise. While it lacks executable code (appropriate since this is an architecture/design skill, not a coding skill), the guidance is specific and directly usable.

The 8-step workflow is clearly sequenced with logical progression from goal-setting through implementation to reporting. It includes explicit validation checkpoints (step 5 audit, mandatory design gates, and the instruction to stop and revise during coding if pass-through APIs or leakage are detected). The feedback loop of 'if answers are weak, revise the design before coding' is explicit.

The skill provides a clear overview with well-signaled one-level-deep references to detailed materials: `references/decision-rules.md`, `references/review-checklist.md`, `examples/module-design-examples.md`, `templates/design-brief.md`, and `templates/architecture-critique.md`. The main file stays at the right level of abstraction while pointing to specifics.