Conciseness

The body is code-forward and lean — every code block teaches the pattern rather than re-explaining concepts Claude already knows (no "what is dependency injection" padding). It falls short of 5 mainly because "When to Activate" and "When to Use" are near-duplicate bullet lists restating the same triggers twice, which could be trimmed.

Actionability

The guidance is mostly executable, real Swift: concrete protocols, default implementations, a mock with configurable errors, default-parameter injection, and Swift Testing tests. Minor gaps keep it below the copy-paste-ready 5 anchor: the `Purpose` type, `MockFileSystemProvider` (used in two tests), and `manager.loadData()` are referenced but never defined.

Workflow Clarity

The five numbered sections (define protocols → default implementations → mocks → inject via default parameters → write tests) form a clear, correctly sequenced workflow. It lacks the explicit validation checkpoints of the 5 anchor, but since this is a design pattern rather than a destructive or batch operation, the validation cap does not apply and the sequence itself is unambiguous.

Progressive Disclosure

Well-organized section headers, coherent single-topic flow, and no buried or nested references (no bundle files exist, and the body references none). It misses 5 because the ~190-line body is above the simple-skill threshold where organization alone earns full marks, and some material (e.g., the full test examples or anti-pattern elaboration) could plausibly live in reference files.

Specificity

The description lists several concrete actions — "mock file system, network, and external APIs using focused protocols and Swift Testing" — grounded in a named domain ("testable Swift code"). It falls just short of the 5 anchor because coverage has minor gaps (e.g., error-path testing, a key emphasis of the skill, is not mentioned) and "network" is asserted without a corresponding concrete action example.

Completeness

It explicitly answers both questions: what ("Protocol-based dependency injection for testable Swift code — mock file system, network, and external APIs using focused protocols and Swift Testing") and when ("Use when Swift code needs testing and file system, network, or external APIs must be mocked"), with concrete trigger phrases matching the 5 anchor exactly.

Trigger Term Quality

Good keyword coverage with natural terms users would say: "Swift", "testable", "mock", "file system", "network", "external APIs", "dependency injection", "Swift Testing". A few natural variations are missing ("unit test", "stub", "XCTest", "test doubles"), keeping it below the comprehensive-synonym coverage of the 5 anchor.

Distinctiveness Conflict Risk

The niche is clear and narrow — Swift protocol-based dependency injection for testing — with distinct triggers (Swift, mock, protocol, Swift Testing). It is unlikely to fire for non-Swift or non-testing skills, matching the 5 anchor ("clear niche with distinct triggers; minimal conflict risk").