DESIGN.md Skill

DESIGN.md is Google's open spec (Apache-2.0,

google-labs-code/design.md

) for describing a visual identity to coding agents. One file combines:

YAML front matter — machine-readable design tokens (normative values)
Markdown body — human-readable rationale, organized into canonical sections

Tokens give exact values. Prose tells agents why those values exist and how to apply them. The CLI (

npx @google/design.md

) lints structure + WCAG contrast, diffs versions for regressions, and exports to Tailwind or W3C DTCG JSON.

When to use this skill

User asks for a DESIGN.md file, design tokens, or a design system spec
User wants consistent UI/brand across multiple projects or tools
User pastes an existing DESIGN.md and asks to lint, diff, export, or extend it
User asks to port a style guide into a format agents can consume
User wants contrast / WCAG accessibility validation on their color palette

For purely visual inspiration or layout examples, use

popular-web-designs

instead. For process and taste when designing a one-off HTML artifact from scratch (prototype, deck, landing page, component lab), use

claude-design

. This skill is for the formal spec file itself.

File anatomy

---
version: alpha
name: Heritage
description: Architectural minimalism meets journalistic gravitas.
colors:
  primary: "#1A1C1E"
  secondary: "#6C7278"
  tertiary: "#B8422E"
  neutral: "#F7F5F2"
typography:
  h1:
    fontFamily: Public Sans
    fontSize: 3rem
    fontWeight: 700
    lineHeight: 1.1
    letterSpacing: "-0.02em"
  body-md:
    fontFamily: Public Sans
    fontSize: 1rem
rounded:
  sm: 4px
  md: 8px
  lg: 16px
spacing:
  sm: 8px
  md: 16px
  lg: 24px
components:
  button-primary:
    backgroundColor: "{colors.tertiary}"
    textColor: "#FFFFFF"
    rounded: "{rounded.sm}"
    padding: 12px
  button-primary-hover:
    backgroundColor: "{colors.primary}"
---

## Overview

Architectural Minimalism meets Journalistic Gravitas...

## Colors

- **Primary (#1A1C1E):** Deep ink for headlines and core text.
- **Tertiary (#B8422E):** "Boston Clay" — the sole driver for interaction.

## Typography

Public Sans for everything except small all-caps labels...

## Components

`button-primary` is the only high-emphasis action on a page...

Token types

Type	Format	Example
Color	`#` + hex (sRGB)	`"#1A1C1E"`
Dimension	number + unit ( `px` , `em` , `rem` )	`48px` , `-0.02em`
Token reference	`{path.to.token}`	`{colors.primary}`
Typography	object with `fontFamily` , `fontSize` , `fontWeight` , `lineHeight` , `letterSpacing` , `fontFeature` , `fontVariation`	see above

Component property whitelist:

backgroundColor

textColor

typography

rounded

padding

size

height

width

. Variants (hover, active, pressed) are separate component entries with related key names (

button-primary-hover

), not nested.

Canonical section order

Sections are optional, but present ones MUST appear in this order. Duplicate headings reject the file.

Overview (alias: Brand & Style)
Colors
Typography
Layout (alias: Layout & Spacing)
Elevation & Depth (alias: Elevation)
Shapes
Components
Do's and Don'ts

Unknown sections are preserved, not errored. Unknown token names are accepted if the value type is valid. Unknown component properties produce a warning.

Workflow: authoring a new DESIGN.md

Ask the user (or infer) the brand tone, accent color, and typography direction. If they provided a site, image, or vibe, translate it to the token shape above.
Write
DESIGN.md
in their project root using
```
write_file
```
. Always include
```
name:
```
and
```
colors:
```
; other sections optional but encouraged.
Use token references (
```
{colors.primary}
```
) in the
```
components:
```
section instead of re-typing hex values. Keeps the palette single-source.
Lint it (see below). Fix any broken references or WCAG failures before returning.
If the user has an existing project, also write Tailwind or DTCG exports next to the file (
```
tailwind.theme.json
```
,
```
tokens.json
```
).

Workflow: lint / diff / export

The CLI is

@google/design.md

(Node). Use

npx

— no global install needed.

# Validate structure + token references + WCAG contrast
npx -y @google/design.md lint DESIGN.md

# Compare two versions, fail on regression (exit 1 = regression)
npx -y @google/design.md diff DESIGN.md DESIGN-v2.md

# Export to Tailwind theme JSON
npx -y @google/design.md export --format tailwind DESIGN.md > tailwind.theme.json

# Export to W3C DTCG (Design Tokens Format Module) JSON
npx -y @google/design.md export --format dtcg DESIGN.md > tokens.json

# Print the spec itself — useful when injecting into an agent prompt
npx -y @google/design.md spec --rules-only --format json

All commands accept

for stdin.

lint

returns exit 1 on errors. Use the

--format json

flag and parse the output if you need to report findings structurally.

Lint rule reference (what the 7 rules catch)

```
broken-ref
```
(error) —
```
{colors.missing}
```
points at a non-existent token
```
duplicate-section
```
(error) — same
```
## Heading
```
appears twice

invalid-color

invalid-dimension

invalid-typography

(error)

```
wcag-contrast
```
(warning/info) — component
```
textColor
```
vs
```
backgroundColor
```
ratio against WCAG AA (4.5:1) and AAA (7:1)
```
unknown-component-property
```
(warning) — outside the whitelist above

When the user cares about accessibility, call this out explicitly in your summary — WCAG findings are the most load-bearing reason to use the CLI.

Pitfalls

Don't nest component variants.
```
button-primary.hover
```
is wrong;
```
button-primary-hover
```
as a sibling key is right.
Hex colors must be quoted strings. YAML will otherwise choke on
```
#
```
or truncate values like
```
#1A1C1E
```
oddly.
Negative dimensions need quotes too.
```
letterSpacing: -0.02em
```
parses as a YAML flow — write
```
letterSpacing: "-0.02em"
```
.
Section order is enforced. If the user gives you prose in a random order, reorder it to match the canonical list before saving.
version: alpha
is the current spec version (as of Apr 2026). The spec is marked alpha — watch for breaking changes.
Token references resolve by dotted path.
```
{colors.primary}
```
works;
```
{primary}
```
does not.

Spec source of truth

Repo: https://github.com/google-labs-code/design.md (Apache-2.0)
CLI:
```
@google/design.md
```
on npm
License of generated DESIGN.md files: whatever the user's project uses; the spec itself is Apache-2.0.

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DESIGN.md Skill

When to use this skill

File anatomy

Token types

Canonical section order

Workflow: authoring a new DESIGN.md

Workflow: lint / diff / export

Lint rule reference (what the 7 rules catch)

Pitfalls

Spec source of truth

License

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