Conciseness

The body is efficient and command-dense, but has minor over-explanation that could be trimmed: the citation "Per [grpcurl README](...)" is repeated four times, and the Overview restates grpcurl basics ("can invoke any gRPC method using one of three descriptor sources... and emits JSON responses") that Claude already knows. This matches 'Efficient; minor instances of over-explanation that could be trimmed' rather than level 5's 'every token earns its place', but is clearly above level 3's 'some unnecessary explanation'.

Actionability

Nearly every section delivers copy-paste-ready, executable commands: install variants with a verify step, list/describe/invoke examples for plaintext, TLS, and mTLS, a newline-delimited heredoc for streaming, auth-header invocations, an exit-code if/else script, jq parsing, a full CI workflow YAML, and a protoset generation command. This matches 'Fully executable; copy-paste ready code or commands; specific examples cover the common cases'.

Workflow Clarity

The flow (install → verify → choose descriptor source via decision table → discover → invoke → parse → CI gate) is clearly sequenced with most checkpoints present: `grpcurl -version` verification, explicit exit-code semantics, an if/else error-recovery script extracting the failure code, and a CI smoke gate conditioned on deployment status. It falls short of level 5 because some checkpoints are implicit — e.g., no validation that protoset generation succeeded or that the health check precedes the sample request is left as an uncommented convention.

Progressive Disclosure

The single-file body is well-organized with clear section headers (Overview, When to use, Authoring, Running, Parsing results, CI integration, Anti-patterns, Limitations, References) and a References section that cleanly signals companion material. It matches 'Good structure; most content is appropriately placed; references mostly clear; minor organization gaps' — the full CI workflow YAML and the flag tables could arguably live in reference files to keep SKILL.md leaner, which is what keeps it from level 5.

Specificity

The description lists multiple specific concrete actions — "grpcurl list and describe via reflection or .proto files, unary and streaming calls with JSON input, TLS and plaintext flags, auth headers, and exit codes" — comprehensively covering grpcurl's capability surface (discovery, invocation, security, auth, scripting). It matches the anchor 'Lists multiple specific concrete actions; comprehensive coverage' and exceeds the level-4 example because no meaningful capability category is missing.

Completeness

Both 'what' (list/describe, unary and streaming calls, TLS/plaintext flags, auth headers, exit codes) and 'when' ("Use for any request to call or inspect a gRPC service from the command line or a script, including one quick call and servers without reflection") are explicitly and concretely stated, matching the anchor for a clear dual answer with concrete trigger phrasing. It clearly exceeds level 4, where the 'when' would be less specific.

Trigger Term Quality

Good keyword coverage including natural terms users would say: "gRPC service", "command line", "one quick call", "smoke tests", "CI gates", ".proto files". It falls short of the level-5 anchor because common phrasings like "test a gRPC endpoint", "curl for gRPC", or "health check" are absent, though coverage is noticeably above the 'some relevant keywords but missing variations' level-3 anchor.

Distinctiveness Conflict Risk

The description carves out a clear niche — invoking/inspecting gRPC services from the command line via grpcurl — with distinct triggers that would not fire for sibling skills (load testing via ghz, mocking, streaming test authoring). It matches 'Clear niche with distinct triggers; minimal conflict risk' and is more focused than the level-4 example, which still spans multiple document formats.