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Pick the right way to represent a dataset so a reader gets the finding in three seconds — a catalog of 20+ chart and diagram forms with when-to-use and failure modes, plus the encoding decisions that make any of them readable (takeaway headline, direct labels, kill the axis, highlight-and-mute, show the caveat). Style-agnostic — use with whatever palette or design system the destination already has.
Passed 19 of 22 test cases with the skill, and 8 of 22 without it.
and 11 more in the full report
11 fixed8 passed either way3 still failing0 broke
Tokens, turns and time describe resource use, not a dollar price.
One of 11 test cases the skill fixed. Same model, same prompt, with and without the skill.
We are charting quarterly customer retention percentages that range between 91% and 96%. To emphasize small quarterly fluctuations, the designer set the bar chart vertical scale baseline to start at 90% rather than 0%. How should this layout be structured?
| Checked | Without skill | With skill |
|---|---|---|
| Recommends switching to a dot plot layout when a zero baseline is omitted. | Passed | Passed |
| Prohibits truncating the vertical axis baseline on bar charts. | Missed | Passed |
The instructions your model reads when the skill loads.
A repertoire, not a style. Distilled from Lenny's Newsletter data illustrations (2025-2026 survey issues) — what makes those charts work is not the palette, it's the form selection and the encoding discipline. Both are portable to any visual language.
For the visual layer, use whatever the destination already has: your product's brand
tokens for in-product surfaces, the built-in dataviz skill for palette construction and
accessibility, your house style for personal sites. This skill decides what shape the data
takes — the layer above color.
| What the data does | Reach for | Form # |
|---|---|---|
| One question, 3-6 ordered answers | Ordered column · Waffle · Nested bands | 1 · 6 · 7 |
| One question, many multi-select answers | Ranked bar · Valence bar | 3 · 4 |
| Same metric, two points in time | Paired columns · Slope | 2 · 9 |
| Same metric, 3+ points in time | Time-series area · Bump | 13 · 18 |
| One metric across 7-10 ordered buckets | Staircase column | 14 |
| One metric across many unordered segments | Small multiples · Dot plot | 8 · 17 |
| Signed score (-100…+100, net, delta) | Diverging bar | 5 |
| Two groups compared across many rows | Dumbbell | 16 |
| Agreement / Likert across several statements | Centered stacked row | 19 |
| Segments × several metrics | Pill matrix | 10 |
| Open-text answers | Word cloud · Coded theme bar | 11 · 3 |
| A relationship the numbers can't carry | Metaphor diagram · Two-column flow | 12 · 20 |
| A named segmentation from clustering | Persona cards | 15 |
| Two dimensions, few labeled points | Named-quadrant scatter | 21 |
Full catalog with mockups and failure modes: references/forms.md.
1. Write the takeaway before you pick a form. Finish the sentence "The point of this chart is ___." If you can't, you have a table, not a chart, and no form will save it. That sentence becomes the headline. Two legal headline modes:
test cases passed, vs 8 / 22 without
More skills from the same source and nearby in the registry, with their headline benchmark lift.