Conciseness

The body is mostly token-dense reference material (tables of API replacements, a 30-item prioritized list) rather than concepts Claude already knows, but the inline/full-scan mode guidance and the isolated-worktree rationale are repeated nearly verbatim across the "Orchestration mode" paragraph, the Modes section, and Workflow steps 6-7. Anchor 3 fits: efficient overall with sections that could be tightened; not 4 because the duplication is more than minor trimming.

Actionability

Concrete executable guidance throughout: specific commands ("go mod tidy", "go test ./...", golangci-lint with the modernize linter), a worked `.modernize` file format example, and exact API mappings ("reflect.PtrTo → PointerTo", "math/rand → math/rand/v2"). Not 5 because before/after code examples for common cases are deferred to references/versions.md rather than shown inline; not 3 because what is inline is directly executable, not pseudocode.

Workflow Clarity

The 9-step workflow has a clear sequence with explicit validation checkpoints: run golangci-lint and go test (step 5), verify dependency compatibility with go mod tidy plus the test suite (step 8), handle stdversion hits by bumping or reverting, and a Go 1.27 risk checklist for the version bump. Not 5 because there is no explicit re-validate/fix loop after applying full-scan changes in the worktree (merge review is implied but not a feedback step); well above 3 since checkpoints are explicit, not implicit.

Progressive Disclosure

Both referenced files exist with matching content, are clearly signaled ("For detailed before/after examples... see [Go version modernizations](./references/versions.md)"), and are one level deep with well-kept overview material in the body. Not 5 because the deprecated-packages migration table and changelog link table overlap versions.md's territory and some pointers are repeated across sections, leaving minor organization gaps against the anchor-5 ideal.

Specificity

"Modernize Golang code to use recent language features, standard library improvements, and idiomatic patterns" names the domain with a single action verb and three thematic areas rather than several concrete operations. Not 4 because it lacks an action list like "extracts text, fills forms, converts pages"; not 2 because the domain and action are concrete, not generic.

Completeness

Explicitly answers both: what ("Modernize Golang code to use recent language features, standard library improvements, and idiomatic patterns") and when ("Use when reviewing Go code with old-style patterns, when encountering a deprecation warning, or when the user asks for modernization, a Go version upgrade..., or a CI/tooling refresh"), with concrete trigger phrases and an explicit exclusion clause. Matches the anchor-5 example's structure.

Trigger Term Quality

Strong natural phrases users would say: "reviewing Go code with old-style patterns", "deprecation warning", "modernization", "Go version upgrade", "CI/tooling refresh". Not 5 because it misses common synonyms and file-extension triggers (e.g. ".go files", "Go migration", "update Go") present in the anchor-5 example.

Distinctiveness Conflict Risk

Clear niche (Go modernization) with distinct triggers, plus an explicit negative scope — "Not for structural refactors, extracting functions, or moving code between packages" with a redirect to a sibling refactoring skill. Minimal conflict risk, matching anchor 5.