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

| 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 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

Or run directly:

npx @google/design.md lint DESIGN.md

All commands accept a file path or - for stdin. Output defaults to JSON.

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 (tailwind, dtcg).

npx @google/design.md export --format tailwind DESIGN.md > tailwind.theme.json
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 | tailwind | dtcg | required | Output format |

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 seven 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 |

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 theme config — npx @google/design.md export --format tailwind DESIGN.md
• 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.