Conciseness

The same 11 pitfalls are covered three times within the body: the 'Best Practices Summary' numbered list, the detailed sections, and the 'Common Mistakes' table — the table's Fix column largely restates the section guidance. This is more than minor trimming, matching 'mostly efficient but includes some unnecessary explanation or could be tightened' rather than the anchor-4 'minor instances'. It is not a 2 because the individual code examples are compact, idiomatic ✗/✓ pairs with no padding.

Actionability

Every pitfall comes with a concrete, executable ✗/✓ Go code pair (e.g., the full slice expression `append(a[:len(a):len(a)], 4)`, the bounds check against `math.MaxInt32`, the extracted `processOne` function for defer-in-loop), plus a nil-behavior table and named linters. Code is copy-paste ready and covers the common cases; not a 4 because no example is pseudocode or missing key details.

Workflow Clarity

This is a reference/catalog skill, and the structure (summary → topic sections → mistake table → cross-references) makes it unambiguous what to check and how to apply each fix, with linter enforcement as a verification backstop. It falls short of 5 because there is no explicit procedure for conducting a review (e.g., an ordered checklist or how to sequence manual checks with `golangci-lint`), and no validation feedback loop, though the domain is non-destructive so the cap-3 rule does not apply.

Progressive Disclosure

Both referenced files exist (`references/nil-safety.md`, `references/slice-map-safety.md`) and are clearly signaled as bold one-level-deep 'Deep Dive' links, matching good structure. It is not a 5 because only 2 of roughly 8 topics are split out — numeric, resource, immutability, and initialization safety live entirely inline — so the split is partial rather than 'content appropriately split' across the whole skill.

Specificity

The description lists eight concrete capabilities ('nil panics, typed-nil interfaces, `append` backing-array aliasing, silent int64-to-int32 truncation, float `==` comparison, `defer` inside loops, defensive copies of slices and maps, usable zero values'), matching the 'multiple specific concrete actions; comprehensive coverage' anchor. It is not a 4 because there are no meaningful coverage gaps — every major defensive-coding category is named.

Completeness

It explicitly answers both questions: the 'what' is the enumerated list of defensive-coding capabilities, and the 'when' is a concrete 'Use when...' clause with multiple trigger scenarios, plus explicit 'Not for...' exclusions. This matches the anchor-5 example structure exactly.

Trigger Term Quality

Natural user phrases are covered with synonyms: 'panics on a nil map write or nil pointer dereference', 'reviewing code for nil-safety', 'numeric conversion overflow', 'resource lifecycle', 'designing a type whose zero value must be safe'. These are exactly what a user would say when needing this skill, matching the comprehensive-synonyms anchor; there is no missing common variation.

Distinctiveness Conflict Risk

It carves a clear niche (accidental-bug safety, 'Security handles attackers; safety handles ourselves' implied via the exclusion list) and explicitly redirects adjacent intents to sibling skills ('→ golang-concurrency', '→ golang-security', '→ golang-troubleshooting'). Conflict risk is minimal because the boundaries are stated, not left implicit.