Conciseness

The body is noticeably verbose for a skill: the same Option-chain example appears three times (getUserCity, 'Simple Null Checks', getManagerEmail), pedagogical padding recurs ('Read this first', 'FP is a tool, not a religion', 'don't rush'), and 'plain language translations' re-explain basic fp-ts API Claude already knows. It is above anchor 1 because the examples are concrete code rather than prose padding, but well below anchor 3's 'mostly efficient'.

Actionability

Guidance is mostly executable: real TypeScript with imports, before/after pairs, and a cheat sheet covering common cases. Minor gaps keep it from 5 — several examples call undefined helpers (fetchUserTE, fetchOrderTE, validateOrderTE, processPaymentTE), section 4 declares 'const doubled' twice, and the callback-hell refactor's fetchUser is never shown returning a TaskEither.

Workflow Clarity

This is a decision guide rather than a multi-step operational workflow, and no destructive or batch operations exist that would require validation checkpoints. Decision rules are explicit and well-sequenced ('When to use pipe / When to skip pipe', 'When NOT to Use FP', the readability rule with too-clever/just-right comparisons). It falls short of 5 because there is no explicit process or verification guidance for adopting the refactors.

Progressive Disclosure

Section headers and navigation within the single file are good, but the skill is monolithic: ~600 lines all inline in SKILL.md with no bundle files, and clearly separable content (the refactor catalog, quick wins, and cheat sheet) is inlined where one-level-deep reference files would serve better. Not anchor 2 because the structure is far from minimal — headers are abundant and consistent — but the inline bulk keeps it at 3.

Specificity

The description names the domain ("guide to fp-ts functional programming") but offers no concrete actions or capabilities — "guide" and "the 80/20 approach" are generic framing, matching the anchor 'Names the domain but actions are minimal or generic'. It cannot score 3 because no 1-2 concrete actions (e.g., 'chain operations with pipe', 'handle nullables with Option') are stated.

Completeness

Both parts are explicitly present: what ("a practical, jargon-free guide to fp-ts functional programming - the 80/20 approach") and when ("Use when writing TypeScript with fp-ts library"). The 'when' could be more specific about scenarios (nullable handling, error handling, async), keeping it at anchor 4 rather than 5.

Trigger Term Quality

Includes the strong natural terms "fp-ts", "functional programming", and "TypeScript" — the phrases a user would naturally say. Missing a few common variations users might use, such as "Option", "Either", "error handling", or "nullable values", so it does not reach comprehensive coverage.

Distinctiveness Conflict Risk

fp-ts is a narrow, clearly named niche; the library-name trigger makes it unlikely to fire for general TypeScript or other FP skills. This matches 'Clear niche with distinct triggers; minimal conflict risk'.