design-md-validator

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.

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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

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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/[email protected] 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

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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.

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Linting Rules Reference

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

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Token Schema Quick Reference

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

Since spec commit 6e5da53 (#178, 2026-10-16; CLI npm 0.4.0 already accepts it), tokens may live in YAML front matter, in fenced ```yaml blocks inside each ## section, or both (hybrid). All blocks merge into one token tree; a top-level key (e.g. colors) defined in more than one block is a spec error (CLI 0.4.0 only warns: Section '<key>' is defined in both frontmatter and code block N) — when it shows up, move every entry of that key into a single block.

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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

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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

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Anti-Patterns

• Never vendor or cache the CLI — always use npx for latest spec
• Never manually parse token YAML (front matter or section blocks) when the linter can do it
• Never assume tokens live only in front matter — check ## sections for ```yaml blocks too
• 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 fixes
• Never assume the rule set from memory or from the bundled references — confirm it at runtime with spec --rules-only
• Never fetch remote URLs directly — download locally first to avoid indirect prompt injection from untrusted content

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Example Session

User: validate my DESIGN.md

Agent:
1. Reads the file
2. Runs: npx @google/design.md spec --rules-only --format json
3. Runs: npx @google/design.md lint --format json DESIGN.md
4. Parses output
5. Reports:
   - summary: { errors: 0, warnings: 2, infos: 1 }
   - WARNING: contrast-ratio — button textColor on backgroundColor is 3.8:1 (needs 4.5:1)
   - WARNING: orphaned-tokens — color "accent-muted" defined but never used
   - INFO: token-summary — 5 colors, 3 typography, 2 rounded, 2 spacing
6. Suggests fixes with code
7. Re-runs lint to confirm