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DESIGN.md
A format specification for describing a visual identity to coding agents. DESIGN.md gives agents a persistent, structured understanding of a design system.
The Format
A DESIGN.md file combines machine-readable design tokens (YAML front matter) with human-readable design rationale (markdown prose). Tokens give agents exact values. Prose tells them why those values exist and how to apply them.
name: Heritage colors: primary: "#1A1C1E" secondary: "#6C7278" tertiary: "#B8422E" neutral: "#F7F5F2" typography: h1: fontFamily: Public Sans fontSize: 3rem body-md: fontFamily: Public Sans fontSize: 1rem label-caps: fontFamily: Space Grotesk fontSize: 0.75rem rounded: sm: 4px md: 8px spacing: sm: 8px md: 16px
Overview
Architectural Minimalism meets Journalistic Gravitas. The UI evokes a premium matte finish — a high-end broadsheet or contemporary gallery.
Colors
The palette is rooted in high-contrast neutrals and a single accent color.
- Primary (#1A1C1E): Deep ink for headlines and core text.
- Secondary (#6C7278): Sophisticated slate for borders, captions, metadata.
- Tertiary (#B8422E): "Boston Clay" — the sole driver for interaction.
- Neutral (#F7F5F2): Warm limestone foundation, softer than pure white.
An agent that reads this file will produce a UI with deep ink headlines in Public Sans, a warm limestone background, and Boston Clay call-to-action buttons.
Getting Started
Validate a DESIGN.md against the spec, catch broken token references, check WCAG contrast ratios, and surface structural findings — all as structured JSON that agents can act on.
npx @google/design.md lint DESIGN.md
{ "findings": [ { "severity": "warning", "path": "components.button-primary", "message": "textColor (#ffffff) on backgroundColor (#1A1C1E) has contrast ratio 15.42:1 — passes WCAG AA." } ], "summary": { "errors": 0, "warnings": 1, "info": 1 } }
Compare two versions of a design system to detect token-level and prose regressions:
npx @google/design.md diff DESIGN.md DESIGN-v2.md
{ "tokens": { "colors": { "added": ["accent"], "removed": [], "modified": ["tertiary"] }, "typography": { "added": [], "removed": [], "modified": [] } }, "regression": false }
The Specification
The full DESIGN.md spec lives at docs/spec.md. What follows is a condensed reference.
File Structure
A DESIGN.md file has two layers:
YAML front matter — Machine-readable design tokens, delimited by --- fences at the top of the file.
Markdown body — Human-readable design rationale organized into ## sections.
The tokens are the normative values. The prose provides context for how to apply them.
Token Schema
version:
Token Types
Type Format Example
Color Any CSS color (hex, rgb(), oklch(), named, etc.) "#1A1C1E", "oklch(62% 0.18 250)"
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 example above
Section Order
Sections use ## headings. They can be omitted, but those present must appear in this order:
Section Aliases
1 Overview Brand & Style
2 Colors
3 Typography
4 Layout Layout & Spacing
5 Elevation & Depth Elevation
6 Shapes
7 Components
8 Do's and Don'ts
Component Tokens
Components map a name to a group of sub-token properties:
components: button-primary: backgroundColor: "{colors.tertiary}" textColor: "{colors.on-tertiary}" rounded: "{rounded.sm}" padding: 12px button-primary-hover: backgroundColor: "{colors.tertiary-container}"
Valid component properties: backgroundColor, textColor, typography, rounded, padding, size, height, width.
Variants (hover, active, pressed) are expressed as separate component entries with a related key name.
Consumer Behavior for Unknown Content
Scenario Behavior
Unknown section heading Preserve; do not error
Unknown color token name Accept if value is valid
Unknown typography token name Accept as valid typography
Unknown component property Accept with warning
Duplicate section heading Error; reject the file
CLI Reference
Installation
npm install @google/design.md
On Windows, quote the package name if your shell treats @ specially (PowerShell, some terminals):
npm install "@google/design.md"
Or run directly (always resolves from the public npm registry):
npx @google/design.md lint DESIGN.md
On Windows/PowerShell, this direct form can produce no output (or open DESIGN.md in your Markdown editor) because the .md suffix in the design.md bin name collides with the Windows Markdown file association during command resolution. Run the dot-free designmd alias instead — point npx at the package with -p, then invoke designmd:
npx -p @google/design.md designmd lint DESIGN.md
The designmd shim resolves to the same entrypoint and works identically across all platforms.
npm error ENOVERSIONS (“No versions available for @google/design.md”)
The CLI is published as @google/design.md on npm. ENOVERSIONS almost always means npm is not querying the public registry (custom registry= in .npmrc, a corporate mirror that has not synced this package, or a misconfigured @google:registry for the @google scope).
Check your effective registry:
npm config get registry
For a normal install from the internet it should be https://registry.npmjs.org/. After fixing config, retry with npm cache clean --force if a stale 404 was cached.
All commands accept a file path or - for stdin. Output defaults to JSON.
Windows tip: when invoking the CLI directly from a package.json script (rather than through npx), use the designmd alias instead of design.md. The .md suffix in the original bin name confuses Windows command resolution with the file association for Markdown files. The designmd shim resolves to the same entrypoint and works identically across all platforms.
// package.json { "scripts": { "design:lint": "designmd lint DESIGN.md" } }
lint
Validate a DESIGN.md file for structural correctness.
npx @google/design.md lint DESIGN.md npx @google/design.md lint --format json DESIGN.md cat DESIGN.md | npx @google/design.md lint -
Option Type Default Description
file positional required Path to DESIGN.md (or - for stdin)
--format json json Output format
Exit code 1 if errors are found, 0 otherwise.
diff
Compare two DESIGN.md files and report token-level changes.
npx @google/design.md diff DESIGN.md DESIGN-v2.md
Option Type Default Description
before positional required Path to the "before" DESIGN.md
after positional required Path to the "after" DESIGN.md
--format json json Output format
Exit code 1 if regressions are detected (more errors or warnings in the "after" file).
export
Export DESIGN.md tokens to other formats.
npx @google/design.md export --format json-tailwind DESIGN.md > tailwind.theme.json npx @google/design.md export --format css-tailwind DESIGN.md > theme.css npx @google/design.md export --format dtcg DESIGN.md > tokens.json
Option Type Default Description
file positional required Path to DESIGN.md (or - for stdin)
--format json-tailwind | css-tailwind | tailwind | dtcg required Output format
Format Output Description
json-tailwind JSON Tailwind v3 theme.extend config object
css-tailwind CSS Tailwind v4 @theme { ... } block with CSS custom properties
tailwind JSON Alias for json-tailwind
dtcg JSON W3C Design Tokens Format Module
spec
Output the DESIGN.md format specification (useful for injecting spec context into agent prompts).
npx @google/design.md spec npx @google/design.md spec --rules npx @google/design.md spec --rules-only --format json
Option Type Default Description
--rules boolean false Append the active linting rules table
--rules-only boolean false Output only the linting rules table
--format markdown | json markdown Output format
Linting Rules
The linter runs nine rules against a parsed DESIGN.md. Each rule produces findings at a fixed severity level.
Rule Severity What it checks
broken-ref error Token references ({colors.primary}) that don't resolve to any defined token
missing-primary warning Colors are defined but no primary color exists — agents will auto-generate one
contrast-ratio warning Component backgroundColor/textColor pairs below WCAG AA minimum (4.5:1)
orphaned-tokens warning Color tokens defined but never referenced by any component
token-summary info Summary of how many tokens are defined in each section
missing-sections info Optional sections (spacing, rounded) absent when other tokens exist
missing-typography warning Colors are defined but no typography tokens exist — agents will use default fonts
section-order warning Sections appear out of the canonical order defined by the spec
unknown-key warning A top-level YAML key looks like a typo of a known schema key (e.g. colours: → colors:); custom extension keys stay silent
Programmatic API
The linter is also available as a library:
import { lint } from '@google/design.md/linter';
const report = lint(markdownString);
console.log(report.findings); // Finding[] console.log(report.summary); // { errors, warnings, info } console.log(report.designSystem); // Parsed DesignSystemState
Design Token Interoperability
DESIGN.md tokens are inspired by the W3C Design Token Format. The export command converts tokens to other formats:
Tailwind v3 config (JSON) — npx @google/design.md export --format json-tailwind DESIGN.md — emits a theme.extend JSON object for tailwind.config.js. --format tailwind is a backwards-compatible alias.
Tailwind v4 theme (CSS) — npx @google/design.md export --format css-tailwind DESIGN.md — emits a CSS @theme { ... } block using Tailwind v4's CSS-variable token namespaces (--color-, --font-, --text-, --leading-, --tracking-, --font-weight-, --radius-, --spacing-).
DTCG tokens.json (W3C Design Tokens Format Module) — npx @google/design.md export --format dtcg DESIGN.md
Status
The DESIGN.md format is at version alpha. The spec, token schema, and CLI are under active development. Expect changes to the format as it matures.
Disclaimer
This project is not eligible for the Google Open Source Software Vulnerability Rewards Program.
