Conciseness

The body is dense and example-driven with terse rules bullets, but includes tutorial-style restatements Claude already knows ("Swift 5.9+ allows `if` and `switch` as expressions that return values", "Swift 6+ allows specifying the error type a function throws") and repeats inline version pins across sections. This fits 'efficient; minor instances of over-explanation that could be trimmed' better than the lean anchor 5.

Actionability

Every section provides complete, executable Swift (result builder, property wrapper, typed throws, regex, guard examples are all copy-paste ready) paired with concrete rules bullets like "Every branch must produce a value of the same type" and specific API mappings in the Common Mistakes list. Fully executable guidance covering the common cases.

Workflow Clarity

The modernization procedure has explicit validation and a feedback loop ("pin current behavior and evaluation order, make one semantic rewrite, compile the affected module, and run focused fixtures/tests. Fix any change before continuing; repeat until behavior is preserved") plus a Review Checklist. However, this procedure lives only inside the If/Switch section rather than being presented as the general process for all patterns, leaving a minor gap versus the fully sequenced anchor.

Progressive Disclosure

A clear overview with a table of contents, well-organized pattern sections, and two real one-level-deep reference files ([references/swift-patterns-extended.md], [references/swift-attributes-interop.md]) that are verified to exist and contain no further nested references. Deep material (extended patterns, attributes/interop) is appropriately split out with clear signals.

Specificity

Enumerates 12+ concrete capabilities with specific API names ("if/switch expressions (Swift 5.9+)", "typed throws (Swift 6+)", "count(where:), contains(where:), replacing()", "CodingKeys, custom decoding, nested containers"), matching the comprehensive-coverage anchor rather than the minor-gaps anchor.

Completeness

Both what ("Apply modern Swift language patterns and idioms for non-concurrency, non-SwiftUI code" plus enumerated coverage) and when ("Use when writing core Swift code involving generics, protocols, enums, closures, or modern language features") are explicit, with concrete trigger phrases.

Trigger Term Quality

"Use when writing core Swift code involving generics, protocols, enums, closures, or modern language features" plus natural terms like "if/switch expressions", "typed throws", "Regex", "Codable", and the synonym pair "some vs any" give comprehensive natural keyword coverage; no meaningful user phrasing is missing.

Distinctiveness Conflict Risk

Explicitly excludes concurrency and SwiftUI, and routes overlapping work to named siblings ("route deep Codable to swift-codable, detailed formatting/localization to swift-formatstyle, and API naming to swift-api-design-guidelines"), giving a clear niche with minimal conflict risk.