Conciseness

The ~50-line body is lean: no re-explanation of what Vega-Lite or the grammar of graphics is, no padded sections, and every section carries decision content. Not a 5 because there is redundant repetition — 'Default to the highest-level tool that cleanly expresses the needed chart' (Overview) restates Selection Rules and Working Pattern step 3 ('Choose the highest-level grammar that supports the chart without contortions'), and 'Use declarative composition before custom code' repeats the same idea a third time.

Actionability

Selection Rules are genuinely usable routing criteria ('Use Observable Plot for fast exploratory... charts', 'Use Vega-Lite for portable, declarative specs, multi-view composition'), but the Working Pattern stays abstract — 'Normalize the table shape', 'Name the mark, encodings, transforms' are directions rather than executable steps. For a chart-building skill, not even one example spec (Vega-Lite JSON or a Plot call) is shown, leaving the gap between anchor 3 ('some concrete guidance but incomplete') and anchor 4; it is not a 2 because the selection guidance itself is specific and actionable, and not a 4 because no concrete artifact or example accompanies the instructions.

Workflow Clarity

The Working Pattern is a clearly sequenced 7-step process with checkpoints embedded ('Check whether the declarative approach still fits the expected number of simultaneous chart instances', 'Check mobile portrait and optional landscape behavior'). Not a 5 because the checkpoints are advisory 'check whether...' prompts rather than explicit validation steps with pass/fail criteria or an error-recovery loop, and the Output Expectations list is not tied back into the workflow sequence.

Progressive Disclosure

The body is a concise overview with well-organized sections (Overview, Selection Rules, Working Pattern, Output Expectations, References) and clearly signaled one-level-deep references. All three skill-referenced bundle files (references/vega-lite-and-vega.md, references/observable-plot.md, references/when-to-stay-declarative.md) exist and are properly split, and shared-theory references are grouped separately. This matches the anchor-5 example: clear overview, well-signaled references, easy navigation.

Specificity

The description names the domain ("Build data visualizations with declarative grammars") and anchors it with concrete tools ("Vega-Lite, Vega, Observable Plot"), but the action side is a single generic verb — it does not enumerate what the skill actually does (compose specs, transforms, faceting, embedding). It sits between anchor 2 ('names domain, minimal actions') and anchor 4 ('several specific actions'): above 2 because the tool enumeration makes the domain concrete, below 4 because only one action is stated.

Completeness

Both parts are present: the what ("Build data visualizations with declarative grammars") and an explicit when ("Use when the user needs Vega-Lite, Vega, Observable Plot, or grammar-of-graphics reasoning, especially for tabular charts"). The when clause is more specific than the anchor-4 example, but the what is a single thin action rather than the comprehensive multi-action coverage of the anchor-5 example, so it lands between the two anchors — noticeably above the midpoint.

Trigger Term Quality

Strong natural triggers users would actually say: "Vega-Lite", "Vega", "Observable Plot", "grammar-of-graphics", "tabular charts". Not a 5 because common phrasings like "chart spec", "declarative chart", or a comparison trigger ("Vega-Lite vs D3") are absent.

Distinctiveness Conflict Risk

A clear niche with explicit boundary language — "especially for tabular charts that do not require bespoke rendering" actively excludes the adjacent D3/Canvas/WebGL skills. Tool names (Vega-Lite, Vega, Observable Plot) are distinct triggers with minimal overlap risk.