Conciseness

The body is largely lean and code-first ('Elements extend `FASTElement`. Do **not** use the `@customElement` decorator.'), assuming Claude's competence. Minor over-explanation remains, e.g., 'Our stance as a framework library is that certain browser APIs are best avoided...' and the rationale sentence under 'Avoid', which fits anchor 4 rather than 5.

Actionability

Nearly all guidance is executable: concrete import paths, `define()` registration, `html`/`css` tagged templates, a binding-syntax table, and full test patterns. Small gaps keep it at anchor 4: the direct-import test snippet references `Model` and `PropertyChangeNotifier` without importing them, and `await MyElement.define(...)` appears without a wrapping context.

Workflow Clarity

This is a topic-organized pattern reference rather than a multi-step workflow, and its sections are unambiguous, with the testing section clearly sequencing direct-import vs browser-evaluated approaches and stating the `page.evaluate` serializability constraint. It does not reach anchor 5 because no explicit verification guidance exists for applying the patterns.

Progressive Disclosure

There are no bundle files at all, so everything — including secondary reference material like the full binding syntax table, test harness details, and TypeScript idiom deep-dives — is inlined in a ~286-line SKILL.md. Section headers give reasonable structure, matching anchor 3 ('some structure... content that should be separate is inline'), but one-level-deep references would materially reduce the always-loaded footprint.

Specificity

The description lists four concrete capability areas — 'authoring Web Components, writing templates and styles, working with the observable/reactive system, and testing' — with no vague filler. It stops short of anchor 5 because coverage has minor gaps (e.g., module conventions and TypeScript idioms covered in the body are not named).

Completeness

It explicitly answers both questions: 'Use this guide when working on TypeScript changes in the FAST monorepo' (when) followed by a concrete capability list (what). This matches anchor 5; it is not 4 because the trigger clause is explicit and specific rather than merely present.

Trigger Term Quality

It includes natural terms a FAST contributor would actually say — 'TypeScript changes', 'FAST monorepo', 'Web Components', 'templates and styles', 'testing'. A few natural terms are missing (e.g., 'custom elements', 'decorators', '.ts'), so it fits anchor 4 rather than 5.

Distinctiveness Conflict Risk

Scoping to 'the FAST monorepo' with FAST-specific capabilities (observable/reactive system, Web Components) creates a clear niche with minimal risk of firing for unrelated TypeScript skills. This matches anchor 5.