Conciseness

The body is lean (~40 lines), assumes Claude's competence, and conveys non-obvious operational facts (tool failure conditions, parameter names, partial-success behavior) rather than explaining known concepts. Minor trimmable redundancy keeps it from anchor 5: the Quick Start steps substantially duplicate the Workflow section (e.g. 'Prune the candidate table before downloading structures' vs '### 2. Prune before download'), and the single-sentence Overview restates the frontmatter description.

Actionability

Guidance is concrete for an instruction-only skill: named tools (`mp_search_materials`, `mp_download_structure`), named parameters/outputs (`output_csv_rel`, `output_dir`, `mp_id`), and specific behavioral contracts ('fails on empty criteria or empty fields', 'supports partial success', 'use the returned results and errors'). It falls short of anchor 5 because no concrete example of search criteria or a requested-fields set is given — 'Define search criteria and requested fields' and the References note defer to the tool schema instead of showing a worked case.

Workflow Clarity

A clear three-step sequence (search with explicit criteria → prune via the CSV ledger → download only retained candidates) with verification checkpoints present: inspect preview rows, check returned results/errors rather than assuming success, and report partial-download failures in the Output Contract. Anchor 5 is not reached because the error-recovery loop is thin — failures are flagged for 'follow-up' but no retry/fix guidance is given for the batch download step.

Progressive Disclosure

The skill is under 50 lines with no bundle files (references/, scripts/, assets/ do not exist) and no external references are needed; the rubric's simple-skill exception applies and the well-organized sections (Overview, Quick Start, Suggested tools, Workflow, Output Contract, References) earn a 5. The References section is a behavioral pointer to the live tool schema, not a file reference, so there are no broken or deeply-nested reference paths.

Specificity

The description names the domain ("materials discovery and bulk structure selection before slab construction") and lists action areas ("database query strategy, candidate filtering, and export readiness"), but these are abstract noun phrases rather than concrete verb-driven actions, and the actual capabilities (querying Materials Project, downloading structures) are never stated. Base fit was anchor 3; the 'what' is delivered in second-person imperative voice ("Use this skill for...") rather than third person, which the rubric penalizes by 1, landing at 2.

Completeness

The 'what' is present ("materials discovery and bulk structure selection... database query strategy, candidate filtering, and export readiness") though abstractly phrased. The 'when' is only weakly implied by the workflow-position phrase "before slab construction"; there is no explicit 'Use when...' clause or equivalent user-situation trigger, which the guidelines cap at 3. Not anchor 4 because the when-guidance is a pipeline stage, not a trigger condition a user would surface.

Trigger Term Quality

Some relevant domain keywords are present ("materials discovery", "bulk structure selection", "slab construction"), but major natural terms are missing: the central database name "Materials Project"/"MP", "download structures", and common synonyms like "screening" or "candidate shortlisting". This matches 'some relevant keywords but missing common variations or synonyms' rather than anchor 4's fuller coverage.

Distinctiveness Conflict Risk

The niche is clear and specific — pre-slab-construction bulk materials selection in a catalysis/surface-modeling context — with distinct terms like "slab construction" and "bulk structure selection". It sits between anchor 4 and 5: mostly distinct with only minor overlap risk against a hypothetical generic structure-download or slab-construction skill, but the trigger set is not rich enough for anchor 5's 'clear niche with distinct triggers' exemplar.