The content is lean and efficient throughout. It avoids explaining basic concepts Claude already knows (like what a module or API is), instead focusing on specific decision criteria and workflow steps. Every section earns its place by providing actionable design guidance rather than background education.

The skill provides highly concrete guidance: a specific design brief template with fields to fill, a numbered workflow with clear steps, 10 explicit decision-rule questions to answer before coding, and clear triggers for when to stop and revise during implementation. While it doesn't have executable code (appropriate for a design/architecture skill), the guidance is specific and directly actionable.

The 8-step workflow is clearly sequenced with logical progression from goal-setting through design comparison to implementation and reporting. It includes explicit validation checkpoints ('If answers are weak, revise the design before coding') and feedback loops ('stop and revise the design if you introduce a pass-through API, leak implementation details...'). The 10-question audit serves as a design gate before proceeding.

The skill references four external files (decision-rules.md, review-checklist.md, module-design-examples.md, architecture-critique-template.md, design-brief-template.md) with clear signaling and one-level-deep navigation. However, no bundle files were provided, so we cannot verify these references exist or are well-structured. The inline design brief template is appropriately placed, but the repeated references to decision-rules.md in two separate sections could be consolidated.

Lists multiple specific concrete actions: 'creating deep modules, hiding implementation knowledge, avoiding leakage and pass-through APIs, comparing alternative designs, documenting interfaces before coding, and critiquing existing architecture.' These are detailed, actionable capabilities.

Clearly answers both 'what' (designing module boundaries, creating deep modules, hiding implementation knowledge, comparing designs, documenting interfaces, critiquing architecture) and 'when' ('Use before implementing or refactoring software when the task requires designing module boundaries, APIs, layers, abstractions...'). The 'Use when' clause is explicit and upfront.

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', and 'coding' could overlap with general coding skills or refactoring-focused skills. The architecture/design focus is fairly distinct but 'refactoring software' is broad enough to potentially conflict with implementation-focused skills.