design-system – Design & UI skill for AI agents

Design System — Onboarding + Shared Brand Tokens

The design-system skill is the shared brand owner for the markdown-html plugin. Run its onboarding once. Every converter (md-document, md-review, md-slides) reads the resulting config via config_loader.py and applies the same 12 CSS custom properties to its output. Without this, conversions render with placeholder defaults — technically functional but unbranded.

This skill ships exactly three Python tools:

1. onboard.py — interactive (or --defaults / --set / --show / --reset) wizard.

2. config_loader.py — importable customization loader with project > global > defaults precedence and MARKDOWN_HTML_NO_CONFIG=1 bypass.

3. brand_palette_validator.py — WCAG-AA contrast checker + HSL palette deriver.

All three are stdlib-only and contain no LLM calls (deterministic per Path-B discipline).

When to invoke

| Symptom | Action |

|---|---|

| User says "convert this markdown to HTML" for the first time in this workspace | Run python3 markdown-html/skills/design-system/scripts/onboard.py |

| ~/.config/markdown-html/design-system.json doesn't exist OR setup_completed_at is null | Refuse conversion, surface onboarding |

| User wants per-repo brand override | python3 .../onboard.py --scope project |

| User wants to change a single field non-interactively | python3 .../onboard.py --set brand.primary=#FF6B35 |

| User wants to reset and re-onboard | python3 .../onboard.py --reset then re-run |

| User wants zero-touch defaults (CI, ephemeral session) | python3 .../onboard.py --defaults |

| Headless / containerized run that should ignore saved config | MARKDOWN_HTML_NO_CONFIG=1 ... |

Onboarding question set (10 questions)

| # | Key | Choices / Validator | Default |

|---|---|---|---|

| 1 | default_output_dir | path; os.access(parent, os.W_OK) | ./markdown-html-out/ |

| 2 | brand.primary | HEX ^#?[0-9a-fA-F]{6}$ | #0A1628 |

| 3 | brand.accent | HEX or blank (auto-derive) | derive from primary |

| 4 | typography.heading_font | Google Font name (12 safe defaults) | Inter |

| 5 | typography.body_font | Google Font name | Inter |

| 6 | design_style | editorial / technical / minimal / playful | technical |

| 7 | code_theme | light / dark / auto | auto |

| 8 | toc.behavior | sticky-sidebar / collapsible-top / inline / none | sticky-sidebar |

| 9 | company_name | string (may be empty) | "" |

| 10 | logo_url | URL or empty (base64-embedded at render) | "" |

Hard rules

1. WCAG AA body-text contrast must pass. brand_palette_validator.validate() runs after every change. Body text on bg must reach 4.5:1; link on bg must reach 4.5:1. If either fails, onboard.py refuses to save (exit code 4) and tells the user to pick a darker primary, blank brand.bg/brand.text to let derivation pick a safe pair, or override brand.text directly. Canon: WCAG 2.2 §1.4.3.

2. Output directory must be writable. onboard.py walks up the path to find an existing ancestor and checks os.W_OK. Empty or unwritable path → exit code 3. The orchestrator's output_path_resolver.py honors the same rule per-conversion.

3. Customization must change behavior, not sit as decoration. Every consumer (md-document, md-review, md-slides) must read the config and render differently when the user changes design_style, brand.primary, code_theme, or toc.behavior. Decorative-only fields fail the design discipline.

4. Precedence is fixed. Project > global > defaults. The deep-merge preserves nested keys (e.g. you can override brand.primary in a project config without losing typography.heading_font from global).

5. Bypass env exists for a reason. MARKDOWN_HTML_NO_CONFIG=1 is for headless CI, ephemeral test containers, and the autoresearch-style evaluator loops. Never set it silently for an interactive user.

Derived 12-token palette

Once the user's brand is captured, brand_palette_validator.derive_palette() produces 12 CSS custom properties stored under derived_palette in the same config file. Every converter inlines these into its <style> block.

| Token | Purpose | Derivation |

|---|---|---|

| --md-bg | Document background | Primary if dark, near-neutral if vibrant |

| --md-surface | Card / callout / blockquote background | Bg ± 4-6% luminance |

| --md-border | Hairline dividers, table borders | Bg ± 8-12% luminance |

| --md-text | Body text | Off-white on dark bg, near-black on light bg |

| --md-text-muted | Captions, metadata, footers | rgba(text, 0.68) |

| --md-accent | Primary CTA, callout headers, link emphasis | Primary if vibrant, hue-shifted lighter if dark |

| --md-accent-soft | Accent backgrounds, hover states | rgba(accent, 0.14) |

| --md-code-bg | Inline code, fenced block bg | Bg ± 4-5% luminance |

| --md-link | Hyperlinks | Iteratively walked to reach 4.5:1 contrast on bg |

| --md-link-hover | Hover state | Link ± 6-8% luminance |

| --md-success | OK / approved / passed | Green anchored, luminance-matched |

| --md-warn | Caution / nit / TODO | Amber anchored, luminance-matched |

Forcing-question library (Matt Pocock grill-with-docs pattern)

One question per turn, recommended answer, canon citation.

1. What's your brand primary color? Recommended: a HEX you already use in your product or docs — not a stock blue. Canon: Aarron Walter, *Designing for Emotion* (color carries brand affect).

2. Should accent be derived or set? Recommended: derive on first run (hue-shift + lighten produces a coherent companion); set explicitly only if your brand kit specifies one. Canon: Adobe Spectrum, *Color Foundations*.

3. Editorial, technical, minimal, or playful? Recommended: technical for engineering specs/reports, editorial for long-read narratives, minimal for sparse reference docs, playful for marketing/landing content. Canon: Ellen Lupton, *Thinking with Type* (style serves the rhetorical purpose).

4. Sticky-sidebar TOC, or inline? Recommended: sticky-sidebar for documents over 800 words, inline for short reads. Canon: Nielsen-Norman, *Table of Contents Best Practices* (2023).

5. Save to global or per-project? Recommended: global by default (consistent across your work); use --scope project only when this repo has a different brand. Canon: research-ops onboarding pattern, research-ops/CLAUDE.md §8.

Customization in use (worked example)

# First-run onboarding (interactive, walks all 10 questions)
python3 markdown-html/skills/design-system/scripts/onboard.py

# Zero-touch defaults for CI / first-test
python3 .../onboard.py --defaults

# Change just the primary color and design style
python3 .../onboard.py --set brand.primary=#FF6B35 --set design_style=editorial

# Per-repo override
python3 .../onboard.py --scope project --set design_style=minimal

# Reset and re-onboard
python3 .../onboard.py --reset
python3 .../onboard.py

# Inspect the effective config (project > global > defaults)
python3 .../config_loader.py --show
python3 .../config_loader.py --status

# Bypass saved config (returns DEFAULTS only)
MARKDOWN_HTML_NO_CONFIG=1 python3 .../config_loader.py --show

# Spot-check WCAG contrast before committing to a brand
python3 .../brand_palette_validator.py --primary "#FF6B35" --accent "#00D4AA"

Assumptions

1. User has at least one brand HEX they want consistent across their HTML conversions.

2. User accepts a 1-2 minute one-time setup.

3. User is OK with Google Fonts as the typography source (CDN, no local font hosting).

4. WCAG 2.2 AA is the accessibility floor (4.5:1 body, 3:1 large/UI). AAA (7:1) is out of scope.

Non-goals

• Not a full design-token system (Style Dictionary, Theo). Twelve tokens, not a hundred.
• Not a custom-font hosting solution. Google Fonts only.
• Not a dark/light mode switcher in the converters. code_theme: auto handles the prefers-color-scheme case for syntax highlighting; layout palette is single-mode per onboarding.
• Not an accessibility audit suite (use axe-core / pa11y for that). We enforce contrast only.
• Does not transform existing CSS — the derived palette is injected into freshly generated HTML.

Distinct from

• marketing/landing/skills/landing/scripts/brand_palette_validator.py — that script's derive_palette() produces 8 tokens shaped for hero-page rendering (--navy, --teal, --card-bg, --card-border). This script produces 12 tokens shaped for document rendering (sticky surface, hairline border, code bg, link, link-hover, success, warn). Same WCAG + HSL math, different token taxonomy.
• research-ops/skills/clinical-research/scripts/onboard.py — same pattern (interactive + --defaults/--set/--show/--reset/--scope), different question set (clinical alpha/power/dropout vs. brand palette/typography/layout).

Output artifact

~/.config/markdown-html/design-system.json (global) or ./.markdown-html/design-system.json

… (full content is in the download package)