Conciseness

The body is a lean quick reference: an ASCII decision tree, imports with one-word mnemonics ("Maybe exists", "Success or failure"), a one-line patterns table, and two match snippets. There is no padding and no explanation of concepts Claude already knows — every token earns its place, matching anchor 5.

Actionability

Concrete, executable TypeScript throughout: the decision tree resolves every branch (async/error/missing) to a concrete type, and the match examples are valid fp-ts v2 code. Minor gaps keep it below anchor 5: `toError` is used in `E.tryCatch`/`TE.tryCatch` without being imported or defined, and the one-line patterns table entries are fragments rather than complete statements.

Workflow Clarity

This is a simple, single-purpose skill (help choosing and using an fp-ts type) and its single action is unambiguous: the decision tree covers all combinations of async/error/missing and every branch resolves to a definitive answer. No destructive or batch operations exist, so the validation cap does not apply; the simple-skill exception yields a 5.

Progressive Disclosure

A short (~60-line) quick reference with well-organized sections (type selection, imports, one-line patterns, pattern matching) and no bundle files. Nothing here warrants separation into external files, so per the simple-skill exception for short skills with no need for external references, well-organized sections alone score 5.

Specificity

The description names the domain ("Quick reference for fp-ts types") and the trigger clause implies a couple of concrete functions ("which type to use", "decision help", "fp-ts imports"), but the what-statement itself carries no concrete actions and coverage is not comprehensive — pattern matching and one-line patterns from the body are unmentioned. It is above anchor 2 (bare domain naming) but below anchor 4 (several specific actions listed).

Completeness

Both parts are present: a clear what ("Quick reference for fp-ts types") and an explicit when-clause ("Use when user asks which type to use, needs Option/Either/Task decision help, or wants fp-ts imports"). It falls short of anchor 5 because the what is thin and generic — it does not enumerate the concrete capabilities (type decision tree, imports, common patterns) the way the anchor-5 example does.

Trigger Term Quality

Natural user phrasings are present — "which type to use", "Option/Either/Task decision help", "fp-ts imports" — which a user needing this skill would plausibly say. A few natural terms are missing (synonyms like "Maybe", "TaskEither", "functional error handling"), keeping it below anchor 5's comprehensive synonym coverage.

Distinctiveness Conflict Risk

The description is tightly scoped to the fp-ts niche with distinct triggers (fp-ts, Option/Either/Task type names), so it is unlikely to fire for unrelated skills. This matches anchor 5's clear-niche, minimal-conflict profile.