Conciseness

The body is lean and spec-like: operating rules, input forms, output shapes, and an executable invocation, with no explanation of concepts Claude already knows. Minor trimming is possible — the two 'Other accepted object forms' JSON blocks could be merged, and the four separator examples could be cut to two — which matches anchor 4 rather than the every-token-earns-its-place anchor of 5.

Actionability

Fully executable guidance: a copy-paste-ready command ('echo '{"grch38":...}' | python scripts/gtex_eqtl.py'), concrete input schemas with real values, exact output shapes for success and failure, and the precise variantId format 'chr{chrom}_{pos}_{ref}_{alt}_b38'. It is not 4 because there are no gaps — the common invocation cases are all covered with real examples.

Workflow Clarity

This is a simple single-task skill where the entire workflow is delegated to one entry-point script, and the single action is unambiguous: pass JSON on stdin, get one JSON object on stdout. Per the simple-skill exception, a single unambiguous action scores 5; the operation is non-destructive and non-batch, so the validation cap does not apply.

Progressive Disclosure

The body is a concise interface document that points to the real entry-point 'scripts/gtex_eqtl.py', which exists in the bundle; the implementation (including scripts/variant_resolution.py, imported by the entry point) is appropriately split out of SKILL.md. Sections are well-organized and shallow with no nested references, so navigation is trivial. Not 4 because there is no misplaced or inline content that belongs in a separate file.

Specificity

The description lists multiple concrete actions — 'Fetch GTEx single-tissue eQTL associations', 'accepting rsID, GRCh37, or GRCh38 input', 'resolving to the required GRCh38 query for the GTEx v2 API', 'returned as JSON' — with comprehensive coverage of the skill's inputs and output. It uses third person voice throughout, so no voice penalty applies.

Completeness

Both questions are explicitly answered: the 'what' (fetch single-tissue eQTL associations, resolve variant coordinates to GRCh38 for the GTEx v2 API) and the 'when' ('Use when a user wants eQTL associations returned as JSON'). This matches the anchor 5 example with a concrete trigger phrase; not 4 because the 'when' clause is explicit rather than merely adequate.

Trigger Term Quality

Good natural keyword coverage: 'GTEx', 'eQTL associations', 'rsID', 'GRCh37', 'GRCh38', 'variant', 'JSON' — exactly the terms a user needing this skill would say. A few natural synonyms are missing, such as 'SNP' and the spelled-out 'expression quantitative trait loci', which keeps it below the comprehensive-synonyms anchor of 5.

Distinctiveness Conflict Risk

GTEx/eQTL lookup is a clear niche with domain-specific triggers (GTEx, eQTL, rsID, GRCh38) that no general-purpose skill would claim, so conflict risk is minimal. It is not the 4 anchor because there is no meaningful overlap with a closely related skill.