Data Visualization
SkillAI & modelsProduce a chart, graph, dashboard, or any data visualization that reads as one system, elegant, accessible, and consistent in light and dark, BRAND-NEUTRAL, shipping a placeholder palette to swap for your own. Read this BEFORE generating ANY chart (bar, line, area, heatmap, scatter, sparkline, donut), choosing chart colors, building a stat tile / meter / KPI row, or laying out a dashboard. Teaches a design-system-AGNOSTIC method: a form heuristic, a color formula with a runnable validator, mark specs, and interaction rules. The method is invariant; a design system plugs in its own ramps and surfaces. A validated default palette is documented in `references/palette.md`, swap that file's values for your brand's. Triggers on: "chart", "graph", "plot", "data viz", "dashboard", "analytics", "visualize data", "categorical colors", "sequential / diverging palette", "stat tile", "sparkline", "heatmap", "legend", "axis", "tooltip", "chart colors", "color by series".
Available today. Use it from your connected AI after setup.
No other account needed.
Add ahel to your AI once: Claude, ChatGPT, Cursor, Claude Code or Codex. Then ask it to use this.
Then ask your AI: use the Data Visualization skill
What this skill tells your AI
The instructions your AI receives, as published by justinlietz93/perfect_prompts in Prompts/System_Prompts_Leaks/Anthropic/claude-code/skills/dataviz/SKILL.md and read by ahel’s review.
A chart is read by people and executed by you. This skill turns "make it look good" into a procedure with checks, so the result is right by construction rather than by taste.
The method here is design-system-agnostic. Nothing in the procedure, the form
heuristic, the six checks, or the mark specs is specific to one product. A design
system supplies a small set of parameters (its ramps, a categorical order, a
diverging pair, a status palette, a texture, its surfaces, its filter components);
the method consumes them unchanged. A validated default palette is the
reference instance, fully specified in references/palette.md. To target your
brand, read that file's structure and substitute its values — touch nothing else.
The single most important habit: the color part is computable, so compute it. Never eyeball whether a palette is colorblind-safe — run
scripts/validate_palette.js.
The procedure — do these in order
Color comes LAST. Most bad charts pick colors first.
- Pick the form. What is the data's job — magnitude, identity, polarity, a
single headline, change-over-time? The job picks the chart type, and sometimes
the answer is not a chart (a stat tile or hero number). →
references/choosing-a-form.md - Assign color by the job it does. Categorical (identity), sequential
(magnitude), diverging (polarity), or status (state) — each has one rule.
Assign categorical hues in fixed order, never cycled. →
references/color-formula.md - VALIDATE the palette — run the script, don't reason about ΔE.
node scripts/validate_palette.js "<hex,hex,…>" --mode light(relative to this skill's base directory — or load it as<script type="module">in the chart's own page, where it readsdata-paletteoff<body>and logs aconsole.tablereport). It returns pass/fail on the lightness band, chroma floor, adjacent-pair CVD separation, the normal-vision floor, and contrast. Fix anything that FAILs before continuing. Re-run for--mode darkwith that mode's surface. - Apply mark specs & spacers. Thin marks, 4px rounded data-ends anchored to
the baseline, 2px lines, ≥8px markers, a 2px surface gap between fills (stacked
segments and adjacent bars alike) and a 2px surface ring on overlapping marks,
selective direct labels. →
references/marks-and-anatomy.md - Add the hover layer — by default. An HTML/SVG chart is interactive; ship
a crosshair+tooltip on line/area and a per-mark hover tooltip on bar/dot/cell.
The only form that skips it is a bare stat tile with no plot. Hit targets bigger
than the mark; filters in one row above the charts. →
references/interaction.md - Final accessibility pass. For ≥ 2 series a legend is always present and ≤ 4 are also direct-labeled (a single series needs no legend box — the title names it), so identity is never color-alone; a table view exists; dark mode is selected — its own steps from the same ramps, validated against the dark surface, not an automatic flip; texture is available for the CVD/print/forced-colors case.
- Render it and look at it. The validator checks color, not layout — open or screenshot the output and eyeball it for label collisions, geometry, and overflow before calling it done.
Then check the result against references/anti-patterns.md — it is the catalog
of what goes wrong. If your chart matches an entry, it's wrong.
Non-negotiables (true in every design system)
- Assign categorical hues in fixed order, never cycled. A 9th series is never a generated hue — it folds into "Other," small multiples, or composite encoding.
- One axis. Never a dual-axis chart (two y-scales). Two measures of different scale → two charts, small multiples, or indexed to a common base. (This is the #1 chart mistake — see anti-patterns.)
- Color follows the entity, never its rank. A filter that changes the series count must not repaint the survivors.
- Sequential = one hue, light→dark. Diverging = two hues + a neutral gray midpoint. Never a rainbow; never a hue at the diverging midpoint.
- Run the validator before shipping any categorical palette. CVD ΔE ≥ 8 is the
target (OKLab ×100); 6–8 is a floor that is legal ONLY with secondary encoding. A
normal-vision floor below 15 is a hard FAIL — full-color readers can't tell the
pair apart; re-step it on the adjacent pairlist (secondary encoding does not excuse
this one); under
--pairs allcut series or facet instead — see check 4. A contrast WARN obligates visible labels or a table view — it is not dismissable. - Thin marks; a legend always present for ≥ 2 series (none for one), with selective direct labels (never a number on every point); recessive grid/axes.
- Text wears text tokens, never the series color — values, labels, and legends stay in primary/secondary/muted ink; a colored mark beside them carries identity.
- Status colors are reserved (good/warning/serious/critical) and never reused for "series 4"; they ship with an icon + label, never color alone.
Plugging in a design system
The method is invariant; only these parameters change per system. The reference
instance — every value filled in — is references/palette.md.
| Parameter | What the system provides |
|---|---|
| Ramps | the hue scales (named steps) the palette draws from |
| Categorical theme | the fixed hue order (a named theme); default + alternates |
| Sequential hue | the default single hue for magnitude |
| Diverging pair | two warm/cool poles + a neutral midpoint |
| Status palette | good / warning / serious / critical — steps distinct from categorical |
| Texture fill | one directional hand-drawn fill, used at 45° / 135° |
| Surfaces | light & dark chart-surface colors (the validator needs these) |
| Filter controls | date-range & dimension controls (behavioral spec in interaction.md) |
To onboard a new system: fill those rows, feed its ramps to the validator, and let it snap each slot to the nearest passing step. Structure and rules stay as written.
Reference files
| File | What it answers |
|---|---|
references/choosing-a-form.md | Which chart type / is it even a chart? |
references/color-formula.md | The four jobs, the six checks, snap-to-passing |
references/marks-and-anatomy.md | Mark specs, spacers, labels, figures, hero number |
references/interaction.md | Tooltips & hover, filters & time ranges |
references/components.md | The pieces a chart is made of — build each in plain HTML |
references/anti-patterns.md | What goes wrong — check every chart against this |
references/palette.md | The reference palette instance — every parameter, filled in; swap for your brand's |
scripts/validate_palette.js | Runnable six-checks validator (run it; don't eyeball) |
Signals
- GitHub stars
- 23
- Forks
- 1
- Last commit
- Aug 2026
ahel review
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bundled executables the agent is told to run
Automated review, not a security audit. Ruleset v1+k2.
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data-visualization-justinlietz93- Source
- github.com/justinlietz93/perfect_prompts