Vois Data Visualization Skill

A chart is read by people and built by you. This skill makes the result right by construction: it picks the form from the viewer's job, assigns color by the job it does, builds the states most dashboards forget, and gives you something to check against.

It answers "what should this data look like, and is it honest and usable?" Page structure is vois-patterns, container components are vois-components, token values and motion are vois-tokens, and every word on the screen is righter.

Two modes. BUILD: you're creating a visualization or dashboard. REVIEW: you're evaluating or improving an existing one. The steps differ; the rules are the same.

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BUILD: the order of work

1. Write the spec. One per visualization, following data/chart-spec.schema.json: the question it answers, the audience, the job, the form. If you can't write the question, the chart shouldn't exist [DV-PURPOSE-001].
2. Walk the decision tree (below, in full in references/decision-tree.md). Land on a result node and a form id from data/chart-catalog.json.
3. Check the spec: node scripts/check-spec.mjs spec.json. Fix every FAIL before you write code. --tree <job> lists the forms a job can reach.
4. Record the choice. If a vois_record_component_choice tool is available, call it with job (the viewer's question), componentName (such as ChartContainer + LineChart), alternativesConsidered (other forms from the tree) and reasoning (the tree result id, e.g. CHART-R-LINE-MULTI). If nothing in the tree fits and vois_report_pattern_gap is available, call it with the closest result as attemptedFallback; otherwise say so in your answer.
5. Get tokens. Get the chart roles in references/implementation.md from the workspace tokens (vois_get_tokens if available). Never write a color value, and never invent a missing role: report the gap.
6. Build from one typed config [DV-SUSTAIN-001], following references/implementation.md. Build the dashboard from DASH-* templates and pieces (references/dashboard-patterns.md).
7. Build the states: skeleton, four kinds of empty, error, refetch, partial [DV-STATE-001] through [DV-STATE-007]. Copy goes through righter.
8. Check the code: node scripts/detect.mjs <files>. Then look at it at 320, 640 and 1280px, light and dark, with a keyboard.
9. Record usage (optional): if vois_record_rule_usage is available, call it with the DV-* ids you applied (violated or ambiguous where they weren't met). These calls are telemetry; if one is missing or errors, carry on.

REVIEW: the order of work

Follow references/review-protocol.md: inventory, infer each job, check the form against the tree, run the mechanical checks, run the judgment checks in triage order, check the page as a whole, propose the upgrade, report in data/review-output.schema.json. data/review-checklist.json has a symptom to fix playbook for the 20 most common problems. Don't flag what passes, and list what you couldn't check.

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Decision tree, at a glance

Start with the viewer's job, not the chart. Full tree with every branch: references/decision-tree.md and data/decision-tree.json.

The viewer needs to...	Default form	Branch
Read one number	Stat tile with delta, sparkline if the trend matters. Meter if it's a ratio against a limit	CHART-Q-SINGLE
See change over time	Line (continuous), column (12 or fewer discrete periods), area (volume, zero baseline), step (holds between events)	CHART-Q-TIME
Compare or rank categories	Sorted horizontal bar. Top 10 plus Other past about 12	CHART-Q-COMPARE
See parts of a whole	Donut for 3 to 6 parts, stacked bar to compare across groups, sorted bar past 6	CHART-Q-PART
See how two measures relate	Scatter, heatmap for two categories	CHART-Q-RELATE
See spread or outliers	Histogram for general audiences; box plot only for analysts	CHART-Q-DIST
See stages or flows	Funnel as aligned bars with step conversion; Sankey for 15 or fewer nodes	CHART-Q-FLOW
See where	Choropleth for rates only; ranked bar for counts	CHART-Q-GEO
Look up exact values	Table, with inline sparklines or bars	CHART-R-TABLE

Then run the gates on the result: audience, simpler form, series count, scale, table twin, volume.

Quick reference

Situation	Use	Not
A single current number	Stat tile with a named delta	A one-bar chart, a 2-slice pie [DV-FORM-003]
2 to 4 series, same unit	Multi-line with a legend and end labels	Dual axis [DV-HONEST-002]
Different units or scales	Small multiples with a shared crosshair	Two y-axes on one plot
6 or more series and one is the story	Emphasis: one accent, rest gray [DV-COLOR-009]	Eight hues competing
More than 8 groups	Top 8 plus Other, table for the tail [DV-FILTER-007]	A 16-hue stack with '+11 more'
Part-to-whole, 3 to 6 parts	Donut with the total in the hole	A 9-slice pie [DV-FORM-004]
Bars	Zero baseline, one color for one series [DV-HONEST-001] [DV-COLOR-007]	A truncated axis, a hue per bar
Line that curves	Monotone or linear; step for state [DV-HONEST-005]	Natural spline overshoot
Current period still open	Hatched bar or dashed line, labeled [DV-HONEST-004]	A cliff that is just an unfinished day
Delta on a KPI	Arrow, sign, number, named baseline [DV-CONTEXT-002]	A bare percent, color-only meaning
Value is zero because nothing was collected	A 'collecting data' state [DV-STATE-002]	A flat zero line [DV-HONEST-008]
Trend inside a table row	Axisless muted sparkline [DV-FORM-008]	A mini chart with axes and a legend
Date range	Presets first, comparison beside, timezone shown [DV-FILTER-002]	A calendar only
Every chart needs reading without sight or color	Text alternative, accessibilityLayer, Chart or Table toggle [DV-A11Y-003] [DV-A11Y-004]	A tooltip as the only readout [DV-A11Y-006]

Which dashboard?

Walk DASH-Q-TYPE in references/dashboard-patterns.md.

Reader	Template
A leader scanning in 30 seconds	DASH-EXEC
An operator watching live state	DASH-MONITOR
An analyst asking new questions	DASH-EXPLORER
A weekly or monthly narrative that gets exported	DASH-REPORT
Users assembling their own widgets	DASH-BUILDER
Someone who drilled into one metric	DASH-METRIC-DETAIL

Reusable pieces: DASH-KPI-TILE, DASH-CHART-CARD, DASH-FILTER-BAR, DASH-DATE-RANGE, DASH-STATE-MATRIX, DASH-TABLE-SPARK, DASH-DRILLDOWN, DASH-TOOLTIP.

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The 14 principles

Each one has a full do and don't list in references/principles.md. The headline:

Principle	One line	Do	Don't
DV-PURPOSE Question and audience	One question, one reader	Write the question before the form	Add a chart because the data exists
DV-FORM Simplest form	The viewer's job picks the form	Walk the tree; stat tile for one number	Pie to compare close values; 22-type pickers
DV-HONEST Truthful	One honest axis, marked partials	Zero baseline for bars; hatch the open period	Dual axes, spline overshoot, flat zero for missing
DV-CLARITY Data, not ink	Remove what doesn't help reading	Label the end and the extreme	A number on every point; truncated axis titles
DV-COLOR Color by job	Identity, magnitude, polarity, status	Tokens in fixed order; entity keeps its color	Hex values; a hue per bar; a 9th hue
DV-CONSIST Consistent	Same metric, same look everywhere	One formatter and one period per filter	$1.2M here, 1,200,000 there
DV-CONTEXT Framed	Compare, scope, date	Delta against a named period; labeled targets	A bare number; a hidden chart filter
DV-A11Y Accessible	Works without color, mouse, sight, motion	Text alternative, table twin, 3:1 marks	Tooltip as the only readout; red and green alone
DV-INTERACT Interactive	Crosshair, shared tooltip, legend toggle	Visible click affordance, one card menu	Needing to hit a 2px line
DV-FILTER One slice	One row of filters above the cards	Presets, comparison, URL state	Per-card pickers; skeleton flash on refetch
DV-STATE Every state	Loading, empty (4 kinds), error, stale	Skeleton in final geometry	Full-page spinner; one generic 'No data'
DV-LAYOUT Hierarchy	Filters, hero KPIs, trend, breakdowns, table	One card anatomy	A grid of equal-weight cards
DV-SUSTAIN Built for live data	Typed config, ugly cases handled	One config feeds chart, table and export	Hardcoded demo data
DV-IMPL Vois stack	Primitives, tokens, accessibility defaults	shadcn Chart with a typed config	Inline colors, fixed pixel widths

Non-negotiables

These are required rules a reviewer will FAIL. Everything else is a WARN with a fix.

• One y-axis per chart [DV-HONEST-002]; bars and areas start at zero [DV-HONEST-001].
• Categorical hues in fixed order, never cycled, eight at most [DV-COLOR-003]; chart colors are tokens [DV-COLOR-001]; an entity keeps its color [DV-COLOR-004].
• Color is never the only signal [DV-A11Y-001]; marks 3:1 and text 4.5:1 [DV-A11Y-002].
• Every chart has a text alternative and a table view [DV-A11Y-003] [DV-A11Y-004]; tooltips enhance and never gate [DV-A11Y-006].
• Partial periods, forecasts and missing data look different from the real thing [DV-HONEST-004] [DV-HONEST-008].
• Every KPI has a delta against a named period [DV-CONTEXT-002].
• One filter row above what it scopes, and every card obeys it [DV-FILTER-001] [DV-FILTER-004].
• Skeleton in final geometry on first load, held frame on refetch, errors isolated to the card [DV-STATE-001] [DV-FILTER-008] [DV-STATE-003].
• No hardcoded data in a chart component [DV-SUSTAIN-005].

Taste dials

When the project defines the three taste dials in VOIS.md or DESIGN.md: DENSITY moves the per-view cap from about 6 to 8 up to 10 visualizations and allows analyst forms for analyst audiences; MOTION never exceeds 300ms and always yields to reduced motion [DV-A11Y-008]; VARIANCE can vary card composition but never the form choice or any honesty rule. Dials tune within the rules, never against them.

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Reference files

Generated from data/*.json by scripts/build-reference.mjs, so they can't drift:

File	Use it for
references/principles.md	Do's and don'ts for each principle, and all 114 rules with do, don't, check and evidence
references/decision-tree.md	The full chart-selection tree with a diagram per branch and the gates
references/chart-catalog.md	48 forms: when to use, when not, baseline, limits, color job, build hint
references/dashboard-patterns.md	Six page templates and eight reusable pieces
references/evidence.md	57 real-product screens from Mobbin: what to adopt, what to avoid

Written by hand:

File	Use it for
references/implementation.md	Chart token roles, shadcn Chart and Recharts code, states, table twin, MCP calls
references/review-protocol.md	How to review and improve existing work, with a worked example
references/sources.md	What each source contributed, and what wasn't read

Structured data (query these instead of scanning prose)

File	Keyed by	Holds
data/dataviz-rules.json	DV-<AREA>-NNN	14 principles and 114 rules: severity, enforcement, do, don't, check, sources, evidence
data/decision-tree.json	question and result node ids	The tree as a graph, job entry points, gates
data/chart-catalog.json	FORM-*	48 forms with fit, audience, baseline, color job, build hint
data/dashboard-patterns.json	DASH-*	Templates and pieces: structure, components, rules, evidence
data/evidence.json	MOB-NN	Mobbin observations with lesson and rule ids
data/review-checklist.json		Review steps, severity map, triage order, fix playbook, the loop checklist
data/chart-spec.schema.json		The spec you fill in before coding
data/review-output.schema.json		The shape of a review

Source of truth. The JSON is canonical and the generated references restate it. scripts/dataviz.test.mjs fails CI if an ID in prose has no JSON entry or the reverse.

Scripts

Script	Does
scripts/check-spec.mjs <spec.json>	Checks a chart spec: the 9 spec rules plus form-versus-job reachability in the tree
scripts/check-spec.mjs --tree <job>	Lists every form a job can reach
scripts/detect.mjs <files>	Finds the 15 auto rules in chart code (13 detectors). Add // dataviz-allow: <detector> for a deliberate exception
scripts/build-reference.mjs [--check]	Regenerates, or checks, the generated references
scripts/dataviz.test.mjs	58 tests: detectors, spec checker, data integrity

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Relationship to other skills

vois-patterns first. It decides that the screen is a dashboard or contains data. Come here for what's inside it. vois-components (JOB-VISUALIZE-DATA) routes data jobs here, then picks the containers: Card, Tabs, Popover, Calendar, Table, Skeleton. vois-tokens supplies live token values, motion and hit-area rules. This skill adds chart roles on top and cites DS-A11Y-001, DS-A11Y-002, DS-ANIMATION-001 and DS-ANIMATION-004. righter writes every title, subtitle, tooltip label, empty state and error. This skill says what the state is, never the words. metrics-tagging instruments chart interactions (range change, legend toggle, drill-down, export) when asked. design-rationale explains why a form or color choice is right when someone pushes back.

Checklist before handoff

• Spec written for each visualization and check-spec has no FAIL
• Form reached through the tree (and vois_record_component_choice called, if available)
• Colors are chart tokens in fixed order, checked per mode
• Text alternative, accessibilityLayer, table view, keyboard path
• Tooltip and crosshair, legend for 2 or more series, drill-down affordance
• One filter row with date presets and a named comparison
• Skeleton, four empty cases, error, refetch and partial states built
• detect.mjs run and clean, or each finding justified
• Checked at 320, 640 and 1280px, light and dark
• vois_record_rule_usage called, if available