Conciseness

The body is dominated by lean tables and executable command blocks with no conceptual padding Claude would already know, but a few trimmable elements remain: the marketing intro ("Bun is a fast all-in-one JavaScript runtime built on JavaScriptCore (Safari's engine). It provides 4x faster startup than Node.js on Linux") and duplicated run examples between Quick Start and Running Files. This matches anchor 4 (efficient, minor instances of over-explanation) rather than 5, where every token earns its place.

Actionability

Nearly every section provides copy-paste-ready executable commands — quick start invocations, flag-positioning gotchas, env-file usage, stdin piping, workspace filters, and debugging variants — with real executable code for env access. The Common Errors table maps concrete errors to concrete fixes, covering the common cases as anchor 5 requires.

Workflow Clarity

As a reference skill there is no multi-step workflow requiring sequencing, and under the rubric's simple-skill exception a clear, well-organized single-purpose reference can score high; the Common Errors table provides error-to-fix recovery loops. However, there are no explicit validation checkpoints or feedback loops (none are strictly needed since no destructive/batch operations are involved), placing it at anchor 4 rather than 5's explicit validate-and-retry structure.

Progressive Disclosure

The body is a concise overview with a dedicated "When to Load References" section that signals exactly three one-level-deep references (references/bunfig.md, references/cli-flags.md, references/module-resolution.md), each verified to exist and each with explicit trigger conditions for when to load it. This matches anchor 5 (clear overview, well-signaled one-level-deep references, easy navigation).

Specificity

The description names concrete topics ("bunfig.toml", "watch/hot modes", "env vars", "module resolution") but contains no action verbs — it is a topic list rather than a list of concrete actions like "Run scripts" or "Configure bunfig.toml". It sits between anchor 2 (domain named, actions generic) and anchor 3 (1-2 concrete actions): the specific subjects lift it above 2, but the complete absence of stated capabilities keeps it below 4.

Completeness

"Use for Bun runtime, bunfig.toml..." provides an explicit when-clause, and the topic list implies the what (a reference for these areas). However, the what is only implied — no concrete actions are stated — so it matches anchor 4 (both present, one could be more explicit) rather than 5 (explicit what AND when with concrete trigger phrases). It is above 3 because the trigger guidance is explicit, not weakly implied.

Trigger Term Quality

Includes natural terms users would say when needing this skill: "Bun runtime", "bunfig.toml", "watch/hot modes", "env vars", "CLI flags", "module resolution". A few natural variations are missing (e.g., "run with bun", "hot reload", "bun test"), matching anchor 4 (good coverage, a few natural terms missing) rather than 5's comprehensive synonym list.

Distinctiveness Conflict Risk

"Bun runtime" and "bunfig.toml" anchor a clear niche with minimal conflict risk, but the trailing generic terms "env vars", "CLI flags", and "module resolution" could overlap with Node.js or general JavaScript tooling skills. This matches anchor 4 (mostly distinct, minor overlap risk with closely related skills) rather than 5's fully distinct triggers.