Conciseness

The body is largely lean, rule-first, and free of teaching Go basics, with tight code blocks. It is not a 5 because of minor padding: "Interfaces Belong to Consumers." is immediately restated as "Interfaces MUST be defined where consumed", and the two consecutive composition examples (ReadWriter, then ReadWriteCloser) make the same point twice. Not a 3 because these are isolated instances, not sections of unnecessary explanation.

Actionability

Guidance is mostly executable: copy-paste snippets like `var _ io.ReadWriter = (*MyBuffer)(nil)`, decision tables for embed-vs-named-field and pointer-vs-value receivers, `go vet ./...` diagnostic commands, and a Mistakes→Fix table. It is not a 5 because several illustrative snippets are `{ ... }` stubs (e.g. `func NewService(store UserStore) *Service { ... }`) rather than complete, runnable code; not a 3 because the stubs are minor and the tables/commands are fully concrete.

Workflow Clarity

As a design-pattern reference rather than a sequential process, it provides clear decision structure (MUST/SHOULD rules, a mistakes checklist, a "Diagnose: go vet ./..." step for copylocks), and it involves no destructive or batch operations so the validation cap does not apply. It sits between anchors: better organized than a 3 (checkpoints are present via vet diagnostics and the fix table) but lacks the explicit validate→fix→retry loop of a 5.

Progressive Disclosure

References are well signaled and exactly one level deep — "→ See [Type Assertions & Type Switches](references/type-assertions.md)" and "→ See [Struct Fields: Tags and Copy Safety](references/struct-fields.md)" — and both files exist and are self-contained, so edge-case detail is correctly deferred. It is not a 5 because the ~280-line body inlines substantial material (the full stdlib interface table, both embedding walkthroughs) that could be split out, leaving SKILL.md less of an overview than the anchor describes.

Specificity

The description enumerates eight concrete capabilities — "composition, embedding, type assertions, type switches, interface segregation, dependency injection via interfaces, struct field tags, and pointer vs value receivers" — comprehensive coverage of the Go type-design domain, matching the score-5 anchor for multiple specific concrete actions. It is not a 4 because there are no meaningful gaps in coverage of the skill's declared scope.

Completeness

It explicitly answers both questions: the "what" is the enumerated pattern list, and the "when" is a concrete double trigger — "Use this skill when designing Go types, defining or implementing interfaces, ..." and "Also use when the user asks about ...". This matches the score-5 anchor verbatim and exceeds anchor 4's weaker "when".

Trigger Term Quality

Natural phrases a user would actually say are comprehensively covered: "designing Go types", "defining or implementing interfaces", "embedding structs or interfaces", "writing type assertions or type switches", "adding struct field tags for JSON/YAML/DB serialization", "choosing between pointer and value receivers", plus quoted idioms ("accept interfaces, return structs", "compile-time interface checks"). Not a 4 because no commonly used phrasing in this domain is missing.

Distinctiveness Conflict Risk

The niche is clear (Go struct/interface type design) with distinct technical triggers, but the description claims territory that overlaps closely related sibling skills it itself cross-references — "dependency injection via interfaces" vs a golang-dependency-injection skill, and naming/idiom territory. Minor overlap with closely related skills is exactly the score-4 anchor; not a 5 ("minimal conflict risk") because DI and naming requests could plausibly trigger those siblings instead.