Conciseness

The writing itself is disciplined (terse bullets, no explanation of concepts Claude already knows), but the ~300-line body carries real structural redundancy: the 8 Execution Steps restate the A–L Mandatory Output Structure (Step 4 ≈ Section E, Step 5 ≈ Section F, Step 7 ≈ Sections G/H/I, Step 8 ≈ Sections B/L), the Reference Module Integration map is repeated per-section in the output structure, "Sample Triggers" duplicates the Input Validation examples, and "What This Skill Should Not Do" largely restates Hard Rules. Not 4: the duplication goes beyond minor trimmable instances; not 2: there is no padded prose or unnecessary concept explanation.

Actionability

Concrete, executable guidance throughout: exact out-of-scope redirect text to quote, named estimators with a default ("Default primary estimator: IVW"), specific decision rules ("If instrument count is sparse, explicitly downgrade claim strength", "label it as a candidate source type", Dataset Disclaimer placement), a fully specified A–L output structure, and 8 reference files supplying field-level templates (8-field step template, exact disclaimer text, estimator/parameter tables). Not 5: the body directs Claude to "specify" items like "SNP selection threshold logic" without inline values (delegated to references), and there is no worked example of a completed output section; not 3: the guidance is concrete and near-fully executable, not pseudocode-level.

Workflow Clarity

"Execution — 8 Steps (always run in order)" gives a clear sequence, with a hard input-validation gate ("respond with the redirect below and stop"), validation/claim-tier definition in Step 7, and explicit verification checkpoints in Hard Rules ("If references cannot be directly verified, output no formal citation for that slot"; incomplete output if a reference module is skipped). Not 5: the process (Steps 1–8) and the deliverable (Sections A–L) form two parallel structures the reader must reconcile on their own — the interleaving is never spelled out, a minor clarity gap. Not 3: checkpoints are explicit, not merely implied.

Progressive Disclosure

Model progressive disclosure: the body is a process/output overview, and each of the 8 reference files is mapped to the exact output section it serves ("references/workload-configurations.md → use when generating Section B"); all 8 referenced files exist and contain substantive material, and inspection of the bundle shows references are one level deep with no nested references. Not 4: navigation signals, file placement, and split of overview vs. detail leave no organization gaps.

Specificity

"Generates complete Mendelian randomization study designs", "Covers core two-sample MR design, optional bidirectional follow-up, optional multivariable MR, IV selection logic, ancestry alignment, harmonization, IVW as the default primary estimator, weighted median / MR-Egger / MR-PRESSO / leave-one-out sensitivity analyses, Steiger directionality", and "Always outputs four workload configs (Lite / Standard / Advanced / Publication+)" list multiple specific concrete actions with comprehensive coverage, all in third person. Not 4: coverage of capabilities is comprehensive rather than having minor gaps.

Completeness

Explicitly answers both questions: what ("Generates complete Mendelian randomization study designs... Always outputs four workload configs... with a recommended primary plan, stepwise workflow, method rationale, validation ladder, figure plan") and when ("Always use this skill whenever a user wants to design, plan, or build a Mendelian randomization study — even if phrased as...") with concrete trigger phrases. Not 4: the when-clause is maximally explicit, including edge-case rephrasings, rather than merely present.

Trigger Term Quality

Includes the natural phrases users would actually say, quoted verbatim: "help me write a paper on X", "design an MR study for Y", "I want to test whether A causally affects B using GWAS", plus "design, plan, or build a Mendelian randomization study", "MR", "GWAS", "exposure", "outcome". Not 4: synonym coverage (full term, MR abbreviation, GWAS) plus paraphrased user phrasings is comprehensive rather than missing a few natural terms.

Distinctiveness Conflict Risk

"Mendelian randomization study designs from a user-provided exposure and outcome direction" using "GWAS summary statistics" defines a clear niche with distinct triggers; the trigger requires MR study-design intent, so overlap with generic epidemiology, PRS, or paper-writing skills is minimal. Not 4: the "help me write a paper on X" broadening is explicitly conditioned on MR study design, leaving only minimal conflict risk.