Conciseness

Nearly all content is repo-specific and non-inferable ('per_request' vs 'custom' rate-limiter modes, the '{PREFIX}_COUNT' env var convention, the duplicate 'apiKey' subblock pattern) with no explanation of concepts Claude already knows. Minor trimmable redundancy — the getCost throw-if-missing example appears twice (the full hosting config block and the 'When the API reports cost' block) — places it at anchor 4 rather than anchor 5's every-token-earns-its-place leanness.

Actionability

Fully executable throughout: exact file paths ('tools/types.ts', 'lib/api/contracts/byok-keys.ts', 'blocks/blocks/{service}.ts'), copy-paste-ready TypeScript covering each pricing variant (API-reported cost, computed cost, 'per_request' flat price, gated 'enabled'), a runnable verification command ('bun run check:byok-providers'), and named reference implementations ('tools/image/generate.ts', 'blocks/blocks/google_maps.ts', 'tools/brandfetch/get_brand.ts'). Matches anchor 5's fully executable, common-cases-covered example.

Workflow Clarity

Six steps are explicitly sequenced in the overview table with per-step 'Where' locations, reinforced by a 12-item checklist and the 'bun run check:byok-providers' validation command. However, there is no error-recovery feedback loop (e.g., what to do when the check fails) and no general build/typecheck verification step, matching anchor 4's 'most checkpoints present; minor validation gaps' rather than anchor 5. The workflow is additive code change, not destructive/batch, so the ≤3 cap does not apply.

Progressive Disclosure

A single-file skill with no bundle files (no references/, scripts/, or assets/ exist), organized by a step-indexed overview table, clear step headers, and subsections. All content sits on the 6-step workflow path rather than being reference material that clearly belongs in a separate file, fitting anchor 4's 'most content is appropriately placed; minor organization gaps'; anchor 5 would require well-signaled one-level-deep references, and anchor 3 would require inlined content that should clearly be separate — the edge-case sections (duplicate subblock pattern, rate-limit sizing rationale) are only borderline candidates for extraction.

Specificity

The description names a concrete action — 'Add hosted API key support to a tool' — enriched with concrete mechanics ('Sim provides the key (metered and billed to the workspace)', 'when a user has not brought their own'). This matches anchor 4's specific actions with minor gaps: more concrete than anchor 3's bare 1-2 actions, but single-action scope falls short of anchor 5's comprehensive multi-action enumeration.

Completeness

It explicitly answers both questions: what — 'Add hosted API key support to a tool so Sim provides the key (metered and billed to the workspace) when a user has not brought their own' — and when — 'Use when adding a `hosting` config to a tool under `apps/sim/tools/{service}/`' with a concrete trigger phrase. This matches anchor 5 exactly; anchor 4 would require a less explicit or less specific 'when' clause.

Trigger Term Quality

Natural developer phrasings are present — 'hosted API key support', 'adding a `hosting` config', 'apps/sim/tools/{service}/' — which a user of this codebase would actually say. Missing natural synonyms like 'BYOK' or 'bring your own key' keep it at anchor 4 ('good keyword coverage; a few natural terms missing') rather than anchor 5's synonym-and-extension completeness.

Distinctiveness Conflict Risk

A clear niche with distinct triggers: repo-specific terms ('Sim', '`hosting` config') anchored to a concrete path pattern ('apps/sim/tools/{service}/') make it very unlikely to fire for any other skill. Matches anchor 5's 'clear niche with distinct triggers; minimal conflict risk' — anchor 4's overlap with closely related skills does not apply here.