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:

1. YAML front matter — Machine-readable design tokens, delimited by --- fences at the top of the file.

2. 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: <string>          # optional, current: "alpha"
name: <string>
description: <string>      # optional
colors:
  <token-name>: <Color>
typography:
  <token-name>: <Typography>
rounded:
  <scale-level>: <Dimension>
spacing:
  <scale-level>: <Dimension | number>
components:
  <component-name>:
    <token-name>: <string | token reference>

Token Types

TypeFormatExampleColorAny CSS color (hex, rgb(), oklch(), named, etc.)"#1A1C1E", "oklch(62% 0.18 250)"Dimensionnumber + unit (px, em, rem)48px, -0.02emToken Reference{path.to.token}{colors.primary}Typographyobject with fontFamily, fontSize, fontWeight, lineHeight, letterSpacing, fontFeature, fontVariationSee example above

Section Order

Sections use ## headings. They can be omitted, but those present must appear in this order:

#SectionAliases1OverviewBrand & Style2Colors3Typography4LayoutLayout & Spacing5Elevation & DepthElevation6Shapes7Components8Do'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

ScenarioBehaviorUnknown section headingPreserve; do not errorUnknown color token nameAccept if value is validUnknown typography token nameAccept as valid typographyUnknown component propertyAccept with warningDuplicate section headingError; 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

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 -

OptionTypeDefaultDescriptionfilepositionalrequiredPath to DESIGN.md (or - for stdin)--formatjsonjsonOutput 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

OptionTypeDefaultDescriptionbeforepositionalrequiredPath to the "before" DESIGN.mdafterpositionalrequiredPath to the "after" DESIGN.md--formatjsonjsonOutput 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

OptionTypeDefaultDescriptionfilepositionalrequiredPath to DESIGN.md (or - for stdin)--formatjson-tailwind | css-tailwind | tailwind | dtcgrequiredOutput format

FormatOutputDescriptionjson-tailwindJSONTailwind v3 theme.extend config objectcss-tailwindCSSTailwind v4 @theme { ... } block with CSS custom propertiestailwindJSONAlias for json-tailwinddtcgJSONW3C 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

OptionTypeDefaultDescription--rulesbooleanfalseAppend the active linting rules table--rules-onlybooleanfalseOutput only the linting rules table--formatmarkdown | jsonmarkdownOutput format

Linting Rules

The linter runs nine rules against a parsed DESIGN.md. Each rule produces findings at a fixed severity level.

RuleSeverityWhat it checksbroken-referrorToken references ({colors.primary}) that don't resolve to any defined tokenmissing-primarywarningColors are defined but no primary color exists — agents will auto-generate onecontrast-ratiowarningComponent backgroundColor/textColor pairs below WCAG AA minimum (4.5:1)orphaned-tokenswarningColor tokens defined but never referenced by any componenttoken-summaryinfoSummary of how many tokens are defined in each sectionmissing-sectionsinfoOptional sections (spacing, rounded) absent when other tokens existmissing-typographywarningColors are defined but no typography tokens exist — agents will use default fontssection-orderwarningSections appear out of the canonical order defined by the specunknown-keywarningA 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.