/design-md-validator

name: design-md-validator
description: >
  Validate DESIGN.md files against the official Google specification using the
  `@google/design.md` CLI linter. Works with local files.
  Use when the user wants to lint a DESIGN.md, check spec compliance, find
  broken token references, verify WCAG contrast ratios, diff two versions,
  export tokens to Tailwind or DTCG format, or audit a design system file
  for structural correctness. Trigger on mentions of "validate DESIGN.md",
  "lint DESIGN.md", "check my design.md", "design.md spec compliance",
  "WCAG contrast check", "broken token references", "design token validation",
  "export design tokens", "diff design systems", "design.md audit",
  "@google/design.md", "npx design.md lint", "design system validation",
  "frontmatter tokens", or any request to verify a DESIGN.md file.
metadata:
  author: https://ft.ia.br
  version: "1.3"
  date: 2026-09-16
  repository: https://github.com/fabricioctelles/skills
  license: Apache 2.0
  category: product-verification
  upstream:
    spec: https://github.com/google-labs-code/design.md
    cli: https://www.npmjs.com/package/@google/design.md
    stitch-skills: https://github.com/google-labs-code/stitch-skills

design-md-validator

Validate, lint, diff, and export DESIGN.md files using the official Google `@google/design.md` CLI. Always uses the latest published version from npm — no vendored copy, always up-to-date with the spec.

---

When to Use

| Trigger | Action | |---|---| | User has a DESIGN.md file and wants validation | `lint` | | User wants to compare two versions | `diff` | | User wants to export tokens to Tailwind/DTCG | `export` | | User wants to see the current spec | `spec` | | User shares a URL to a raw DESIGN.md | Download locally first | | User asks "is my design.md valid?" | `lint` + interpret findings |

---

Core Commands

All commands use `npx @google/design.md` to ensure the latest version is always used. Never install globally — `npx` resolves from the public npm registry.

Lint (validate)

npx @google/design.md lint DESIGN.md

Output: JSON with `findings[]` and `summary { errors, warnings, infos }`. Exit code 1 if errors found, 0 otherwise.

Diff (compare versions)

npx @google/design.md diff DESIGN.md DESIGN-v2.md

Output: JSON with token-level changes (added, removed, modified) and regression flag. Exit codes: `0` no regression, `1` regression (errors in "after" > errors in "before"), `2` input failure (file not found or unreadable).

Export (to other formats)

# Tailwind v3 config
npx @google/design.md export --format json-tailwind DESIGN.md

# Tailwind v4 CSS theme
npx @google/design.md export --format css-tailwind DESIGN.md

# W3C Design Tokens (DTCG)
npx @google/design.md export --format dtcg DESIGN.md

# CSS custom properties (optional --prefix)
npx @google/design.md export --format css-vars DESIGN.md
npx @google/design.md export --format css-vars --prefix ds DESIGN.md

`css-vars` shipped in npm 0.4.0 (2026-07-27). Pin with `npx @google/design.md@0.4.0` only if you must freeze the CLI; default `npx` already resolves 0.4.0+.

Spec (output the format specification)

npx @google/design.md spec
npx @google/design.md spec --rules
npx @google/design.md spec --rules-only --format json

---

Workflow

1. Obtain the DESIGN.md

**Local file:**

npx @google/design.md lint ./DESIGN.md

**From URL:** If the user provides a URL to a remote DESIGN.md file, download it locally first before validation.

**From stdin:**

cat DESIGN.md | npx @google/design.md lint -

2. Discover the Active Rule Set

Before interpreting anything, check which rules the installed CLI actually runs — the rule set changes between releases, and the bundled references are a fallback, not the authoritative source:

npx @google/design.md spec --rules-only --format json

3. Run Lint

npx @google/design.md lint --format json DESIGN.md

4. Interpret Findings

Parse the JSON output and report to the user:

| Severity | Meaning | Action | |---|---|---| | `error` | Spec violation — file is invalid | Must fix | | `warning` | Best practice violation — file is valid but suboptimal | Should fix | | `info` | Informational — suggestions for improvement | Nice to fix |

5. Provide Actionable Fixes

For each finding, explain: 1. What the rule checks 2. Why it matters 3. How to fix it with a concrete code example

6. Re-validate After Fixes

After applying fixes, re-run lint to confirm the file passes.

---

Linting Rules Reference

Load `references/linting-rules.md` for the complete rule table when providing detailed explanations of lint failures.

---

Token Schema Quick Reference

Load `references/token-schema.md` for the complete YAML frontmatter schema when helping users author or fix their frontmatter tokens.

---

Windows Compatibility

On Windows/PowerShell, the `.md` suffix in the bin name collides with Markdown file associations. Use the `designmd` alias:

npx -p @google/design.md designmd lint DESIGN.md

---

Related Official Skills

Names below match `google-labs-code/stitch-skills` as of 2026-09-16. `stitch-design-taste` is gone.

| Skill | Plugin | Purpose | |---|---|---| | `generate-design` | stitch-design | New screens, edits, variants in Stitch | | `extract-design-md` | stitch-design | DESIGN.md from frontend source | | `design-md` | stitch-utilities | DESIGN.md from a Stitch project | | `taste-design` | stitch-utilities | Premium / anti-generic DESIGN.md |

Install:

npx skills add google-labs-code/stitch-skills

---

Anti-Patterns

• Never vendor or cache the CLI — always use `npx` for latest spec
• Never manually parse YAML frontmatter when the linter can do it
• Never guess at contrast ratios — let the linter compute them
• Never assume section order is correct — let the linter verify
• Never skip re-validation after fixe