Conciseness

The body is largely policy and house standards rather than teaching basics, and the Go 1.22 loop-variable note is genuinely non-obvious knowledge. However, the constructor snippet ("func NewUserService(store Store, log *slog.Logger)...") and the graceful-shutdown snippet are standard patterns Claude already knows, so a few tokens could be trimmed — fitting 'efficient; minor instances of over-explanation' rather than the every-token-earns-its-place level 5 anchor.

Actionability

Most guidance is concrete and executable: specific validation commands ("go test -race ./...", "golangci-lint run", "go vet ./..."), an errgroup example, and exact error-wrapping formats. But the error-handling snippet will not compile — "errors.Is(err, sql.ErrNoRows)" references an `err` that is never declared because the "row.Scan(&u)" call is missing — a pseudocode-like gap that keeps it below the fully copy-paste-ready level 5 anchor.

Workflow Clarity

The implementation workflow has a clear sequence with an explicit validation checkpoint ("Validate — go test -race ./..., golangci-lint run, go vet ./..."), and the 'Non-negotiable standards' list functions as a checklist. What's missing is an explicit failure-recovery loop ('if validation fails, fix and re-run'), so it matches 'clear sequence with most checkpoints present; minor validation gaps' (4) rather than the feedback-loops-present level 5 anchor. This is not a destructive/batch skill, so the level-3 cap does not apply.

Progressive Disclosure

The body is a well-organized overview: a topic/file/when-to-read table instructs "Load these on demand — read only the file(s) relevant", all five referenced files exist and are substantial one-level-deep references, and sections explicitly defer detail ("Full wiring ... lives in references/concurrency.md"). This matches the clear-overview with well-signaled one-level-deep references anchor.

Specificity

The description lists multiple concrete capabilities — "writing, reviewing, debugging, or designing Go code" and "a second opinion on a Go architecture" — with comprehensive topic coverage ("idiomatic patterns, concurrency, error handling, project structure, performance optimisation, observability, and testing"). Coverage of the Go domain is thorough with no notable gaps, matching the comprehensive anchor rather than the 'minor gaps' level 4 anchor.

Completeness

Both questions are answered explicitly: 'what' via "Senior Go engineer and technical advisor ... Covers idiomatic patterns, concurrency, error handling ..." and 'when' via "Invoke whenever the user is writing, reviewing, debugging, or designing Go code, asking about goroutines, channels, interfaces ...". This mirrors the level-5 anchor's concrete what-and-when structure; the 'Use when...' clause is present, so the level-3 cap does not apply.

Trigger Term Quality

"Triggers on: Go, Golang, goroutine, channel, interface, gRPC, go.mod, go test, pprof, golangci-lint" covers synonyms (Go/Golang), file names (go.mod), commands (go test), and tool names (pprof, golangci-lint) — all phrases a user would naturally say when needing Go help. This matches the comprehensive synonym-and-extension anchor, not merely 'good keyword coverage' at level 4.

Distinctiveness Conflict Risk

The niche is clear (Go) and most triggers (Go, Golang, goroutine, go.mod, pprof) are highly distinct, but the standalone trigger words "channel" and "interface" are generic terms that could overlap with non-Go skills (UI interfaces, messaging channels). This lands on 'mostly distinct; minor overlap risk' (4) rather than the minimal-conflict level 5 anchor, whose example triggers are all unambiguously domain-specific.