Conciseness

The body is dense with opinionated design decisions (exit-code table, TTY decision priority, flag conventions, config precedence) and assumes competence rather than tutoring, but a few background asides could be trimmed: the "Buffering matters..." paragraph explaining OS behavior Claude already knows and "This is a de facto standard across the ecosystem". Not 5: these minor instances of over-explanation keep it from being uniformly lean; not 3: the padding is occasional, not a pattern.

Actionability

Guidance is concrete and executable throughout: exact flags (`--plain`, `--fields`, `--password-file`), exact exit codes, a copy-paste-ready Go `CLIError` struct, the JSON envelope, named libraries (`go-isatty`, `cobra`, `pflag`, `viper`, `adrg/xdg`), and real pipe examples (`mycli list --json | jq '.data[] | select(.status == "failed")'`). Specific examples cover the common design and review cases.

Workflow Clarity

Ordered decision procedures are unambiguous (the 8-step TTY/color priority "first match wins", the 5-level config precedence), and the "Verification checklist" section ("After designing or reviewing a CLI:") provides an explicit validation checkpoint list covering the full contract. Not 4: validation checkpoints are explicit and comprehensive, matching the checklist-for-complex-processes pattern.

Progressive Disclosure

Core design principles live in SKILL.md while specialized concerns (long-running operations, credentials, testing) are split into three real one-level-deep reference files, each clearly signaled with content summaries and "Load when..." triggers, and the top of the file points to that loading guidance. Bundle structure matches the referenced paths exactly. Not 4: the split is appropriate and navigation is easy with no buried references.

Specificity

"stdout/stderr discipline, JSON and plain output modes, semantic exit codes, noun-verb commands, structured errors" lists multiple specific concrete capabilities alongside the core action ("building Unix-composable command-line tools in Go"), with comprehensive coverage of the CLI design domain. Not 4: the enumerated items leave no notable gaps in what the skill covers.

Completeness

The description explicitly answers both questions: what ("Principles for building Unix-composable command-line tools in Go: [five concrete concerns]") and when ("Use when designing, building, or reviewing CLIs") with concrete trigger activities. Not 4: the when-clause is explicit and specific rather than merely present.

Trigger Term Quality

"command-line tools", "CLIs", "Go", and "designing, building, or reviewing" are natural terms users would say, with synonym variation between "command-line tools" and "CLIs". Not 5: common variations like "terminal", "shell tool", or "flag/argument parsing" are absent, so coverage is good but not comprehensive.

Distinctiveness Conflict Risk

"Unix-composable command-line tools in Go" carves out a clear niche with distinct triggers (CLI design/build/review in Go), making conflict with other skills minimal. Not 4: there is no meaningful overlap risk with closely related skills.