Conciseness

The body is lean throughout: a compact decision tree, terse import labels, a token-efficient patterns table, and short pattern-match examples, with no over-explanation of concepts Claude already knows.

Actionability

Snippets like 'O.fromNullable(value)', 'E.tryCatch(() => risky(), toError)', 'TE.tryCatch(() => fetch(url), toError)', and 'pipe(value, fn1, fn2, fn3)' are copy-paste ready and cover the common cases.

Workflow Clarity

As a simple single-purpose reference with no destructive or batch operations, the 'Which Type Should I Use?' decision tree provides a clear, unambiguous sequenced flow, satisfying the simple-skill exception.

Progressive Disclosure

The compact reference is split into four well-organized sections (decision tree, imports, one-line patterns, pattern match) with no need for external files, meeting the under-50-lines/no-external-refs criterion.

Specificity

The 'what' is a single action ('Quick reference for fp-ts types') naming the domain plus a couple of concrete items (Option/Either/Task, imports), but it does not enumerate several distinct concrete actions like the higher anchors require.

Completeness

It clearly states what it does ('Quick reference for fp-ts types') and explicitly when to use it with concrete trigger phrases, matching the anchor that requires both what and when.

Trigger Term Quality

'Use when user asks which type to use, needs Option/Either/Task decision help, or wants fp-ts imports' gives good natural-term coverage with concrete type names; a few synonyms or extensions are missing, keeping it below 5.

Distinctiveness Conflict Risk

fp-ts is a niche library and the description anchors on specific type names (Option/Either/Task), giving a clear niche with distinct triggers and minimal conflict risk.