Conciseness

The body is lean, assumes React/TSX competence, and explicitly avoids re-defining the model ('not a second definition of it'), but a few framing sentences ('This skill and its siblings carry the operational detail...') could be trimmed, so it is efficient with minor over-explanation rather than the every-token-earns-its-place anchor 5.

Actionability

Concrete decision rules ('Before adding custom behavior... look for an existing base component', 'keep the public API identical and surface the structural decisions', 'shipping the narrower, reversible option and asking') plus an illustrative TSX worked example give mostly executable guidance; it stops short of anchor 5 because the example is explicitly non-runnable in the repo.

Workflow Clarity

A loose sequence is present (orient via style.md -> understand the four types -> decide which are needed -> surface the decision) and the core rule (ship the narrower reversible option, ask) is clear, but there are no explicit validation checkpoints or feedback loops in the decision process, matching 'sequence present but checkpoints missing or implicit'.

Progressive Disclosure

It is a clean overview that pushes detail one level deep via clearly signaled references — 'contributor-docs/style.md is the source of truth', the listed sibling skills for 'detailed rules', and 'modular-ds-accessibility-contract' — with content appropriately split and easy to navigate; no bundle files exist to detract from this structure.

Specificity

Lists several concrete use cases ('deciding how to structure a new Primer React component', 'evaluating whether an existing component's API is at the right level of abstraction', 'orienting on the modular design system approach') plus the four named API types, so it sits at 'several specific actions; minor gaps' rather than the fully comprehensive anchor 5.

Completeness

It explicitly answers both — 'Covers how the four API types... relate and compose' (what) and 'Use when: deciding how to structure... or orienting on the modular design system approach before using a more specific modular-ds-* skill' (when) with concrete trigger phrases, matching the anchor that requires both clearly and explicitly.

Trigger Term Quality

Natural Primer-contributor phrases like 'structure a new Primer React component', 'level of abstraction', and 'modular design system' appear with an explicit 'Use when:' clause, giving good keyword coverage, but a few common synonyms/variations a contributor might say are absent so it is not the comprehensive anchor 5.

Distinctiveness Conflict Risk

It carves a clear niche (Primer React, the spectrum-of-abstraction model) and explicitly positions itself 'before using a more specific modular-ds-* skill', but it inherently overlaps with the sibling modular-ds-config/presentational/base/utilities skills it references, leaving minor overlap risk rather than minimal.