web-stylebook-mcp

Design intelligence for AI coding agents. Stop shipping the same hero-plus-three-cards. Your agent gets scored design contracts — directions, interface-design plans, UX-principle plans, UI-state plans, tokens, evidence-backed audit plans — then writes and verifies the code from evidence.

English · 한국어

Coding agents default to the same generic UI because they can't decide what it should look like — so they fall back to hero + 3 cards + a gradient. web-stylebook-mcp is a Model Context Protocol server that hands the agent design contracts — scored visual directions, placement-aware interface-design plans, evidence-labeled UX-principle plans, UI-state plans, and design tokens — drawn from the same curated catalog as webstylebook.com. It returns evidence, not code. Your agent still writes the code — now it knows what to build and what to verify.

No API key. No model call. No network. No project filesystem access. Deterministic, read-only, fully local.

Without it / with it

| | Without web-stylebook-mcp | With web-stylebook-mcp | |---|---|---| | Direction | Guesses one look, commits to it | Scored candidates + reason codes + what it rejected and why | | Craft | Principle names dropped into a doc, nothing verified | Placement guidance + an observable check per principle, cautions attached | | UX evidence | "Hick's Law says…" as a conversation-ender | Evidence-labeled prompts (strong / contextual / contested) you can't restate as law | | UI states | Happy path only; empty / error / loading bolted on later | Required / recommended / domain states up front, per surface | | Tokens | Hand-picked hexes, contrast rarely checked | Role-based tokens with WCAG contrast warnings | | Audit | "Looks good" from a summary | Surface-aware checks with stable ids, severity, required evidence, and explicit unverified states | | Result | Generic AI UI | A defensible design contract the agent builds from |

Watch it decide

"High-density monitoring dashboard for SREs, watched all day on call. Calm, technical. Avoid cyberpunk."

// → recommend_design_direction  (input)
{
  "productDescription": "High-density monitoring dashboard for SREs, watched all day on call",
  "productType": "operational-saas",
  "tone": ["calm", "technical"],
  "density": "high",
  "usageFrequency": "daily",
  "avoid": ["cyberpunk"]
}

// ← result
{
  "confidence": "high",
  "candidates": [                      // all tied at 0.91 — ordering is NOT meaningful
    { "styleId": "notion-style",   "score": 0.91 },
    { "styleId": "platform-core",  "score": 0.91 },
    { "styleId": "quiet-utility",  "score": 0.91 },
    { "styleId": "runtime-signal", "score": 0.91 },
    { "styleId": "console-launch", "score": 0.91 }
  ],
  "rejected": [
    { "styleId": "aurora-gradient",  "reasonCodes": ["PRODUCT_NOT_IDEAL", "DAILY_USE_OVERSTIMULATION"] },
    { "styleId": "claymorphism",     "reasonCodes": ["PRODUCT_NOT_IDEAL"] },
    { "styleId": "cyberpunk-glitch", "reasonCodes": ["EXPLICITLY_AVOIDED", "DAILY_USE_OVERSTIMULATION"] }
  ],
  "pairings": [
    {
      "styleId": "macos-liquid-glass",
      "pairWith": "notion-style",
      "role": ["forms", "navigation", "repetitive surfaces"]
    }
  ],
  "guidance": "Treat candidates as scored evidence; choose using product context. candidates[0] is the strongest match, not a mandate. 5 candidates are tied at the top score — the ordering among them is not meaningful; pick using their \"differentiators\" and your product context."
}

Notice what it doesn't do: it doesn't pretend there's one winner. Five directions tie at 0.91, rejected styles come with reason codes, and pairings are suggestions rather than a mandate. That honesty is the point — the server provides evidence, the agent decides.

Then turn the chosen direction into real tokens:

// → compose_design_tokens(style: "notion-style", format: "css-variables", theme: "light")
// 0 WCAG contrast warnings
:root {
  --color-canvas: #ffffff;
  --color-text:   #37352f;
  --color-accent: #2383e2;
  --color-border: #d3d3d1;
  /* … role-based color, type, spacing, radius, motion, density */
}

One request in — and the agent chose a direction, saw what was rejected and why, and got tokens that pass WCAG, without generating a line of code.

What an agent builds with it

A different brief — "a marketing landing page for Throughline, a B2B SaaS that turns scattered customer feedback (support tickets, sales calls, app reviews, Slack) into one prioritized roadmap." No layout, no hero, no styling was specified. Following the companion skill, the agent composed the opening from the product's core idea instead of reaching for a stock hero: the right half is a bespoke diagram of the product's actual mechanic — feedback sources converging into an auto-ranked roadmap — not a decorative card you could paste onto any other site.

How it works

flowchart LR
    A[AI coding agent] -->|product, tone,<br/>density, usage| B(web-stylebook-mcp)
    B --> C{Bundled catalog<br/>read-only · offline}
    C --> D[recommend_design_direction]
    C --> E[compare_design_directions]
    C --> F[get_design_principle_plan]
    C --> G[get_ux_principle_plan]
    C --> H[get_ui_state_plan]
    C --> I[compose_design_tokens]
    C --> J[get_design_audit_plan]
    D & E & F & G & H & I & J -->|design contracts<br/>scores · reason codes<br/>placement · evidence · tokens| A
    A -->|writes code<br/>from evidence| Z[Your UI]

The agent describes the product; the server scores its curated catalog and returns structured evidence. No code is generated and nothing leaves your machine.

Install

Requires Node ≥ 20.

Use the Codex CLI:

codex mcp add web-stylebook -- npx -y web-stylebook-mcp@latest

Or add it to ~/.codex/config.toml. You can also use a project-scoped .codex/config.toml in a trusted repository:

[mcp_servers.web-stylebook]
command = "npx"
args = ["-y", "web-stylebook-mcp@latest"]

Restart Codex or open a new session after editing config. In the Codex TUI, run /mcp to confirm the server is active.

claude mcp add web-stylebook -- npx -y web-stylebook-mcp@latest

Add to your MCP config:

{
  "mcpServers": {
    "web-stylebook": {
      "command": "npx",
      "args": ["-y", "web-stylebook-mcp@latest"]
    }
  }
}

Add the same block to your claude_desktop_config.json, then restart:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
• Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "web-stylebook": {
      "command": "npx",
      "args": ["-y", "web-stylebook-mcp@latest"]
    }
  }
}

Tools

| Tool | What you get | The honest part | |------|--------------|-----------------| | recommend_design_direction | Scored style candidates with reason codes, rejected styles with why, secondary pairings, confidence | The model makes the final pick — this is the evidence provider | | compare_design_directions | 2–4 directions compared across product-fit, repeated-use, density, trust, distinctiveness, accessibility-risk, motion, maintenance | No single winner is declared | | get_design_principle_plan | A focused placement, application, and verification plan selected by visual concerns, surface, phase, or principle ids — with source references where available | Craft prompts are testable guidance, not empirical laws or a fixed recipe | | get_ux_principle_plan | A focused apply-and-verify plan selected by outcomes, surface, phase, or principle ids — with questions, cautions, confidence, and references | Principles are contextual prompts, not universal laws or a substitute for research | | get_ui_state_plan | Required / recommended / domain UI states for a surface (data-table, form, checkout, chat, developer-console) — triggers, must-show, must-not, a11y, motion | Covers the states agents forget: empty, error, loading, edge | | compose_design_tokens | Role-based tokens (color, type, spacing, radius, motion, density) as json / css-variables / tailwind / typescript, light / dark / both | Emits WCAG contrast warnings instead of hiding them | | get_design_audit_plan | Localized, surface-aware checks with stable ids, severity, applicability, required evidence, remediation, user-facing content checks, selected principle checks, and UI-state coverage | The tool plans the audit but never pretends it inspected your project; missing evidence is NOT_VERIFIED, not PASS |

Catalog: 48 styles · 25 interface design principles · 23 UX principles · 51 structured audit checks · 20 components · 5 surfaces · 57 UI-state recipes · 29 motion profiles · 14 product archetypes.

Localized output

Every tool takes an optional locale. Reason codes, guidance, and labels come back in the requested language:

"en" | "ko" | "ja"     // English · 한국어 · 日本語

Resources

Browse the catalog directly over MCP resources:

webstylebook://manifest
webstylebook://styles · /styles/{id}
webstylebook://motion · /motion/{id}
webstylebook://components · /components/{id}
webstylebook://principles · /principles/{id}
webstylebook://design-principles · /design-principles/{id}
webstylebook://states/surfaces · /states/{surface} · /states/{surface}/{state}
webstylebook://products · /products/{id}
webstylebook://policies/anti-patterns · /policies/verification · /policies/audit-checks

Prompts

Ready-made MCP prompts for common workflows:

design-product · design-screen · complete-ui-states · redesign-with-style · audit-design-direction · audit-design-principles · audit-ux-principles

When audit-design-direction is invoked without an explicit scope, it asks two short questions before inspection: audit coverage (visual / visual + copy and information structure / full experience) and change depth (findings / proposals / implement and verify). File edits, commits, releases, and deployment are never inferred from an audit request.

Content coverage checks more than jargon: it tests whether material claims, conclusions, and recommendations match their support and expressed certainty, whether prominent copy conveys concrete context-specific information, and whether its visual emphasis matches information value, task relevance, and support. Cards, statistics, and Sitemap links are still judged by their actual user-task value rather than banned as types.

CLI

web-stylebook-mcp                 # run the server over stdio (default)
web-stylebook-mcp --version
web-stylebook-mcp --catalog-info
web-stylebook-mcp --validate-catalog

Companion skill

A companion skill ships in skill/ so your agent reaches for these tools at the right moment — and uses the results well (compose, don't recolor; offer multiple candidates; earn trust, don't fake it; land on reusable components):

Codex

• Copy or symlink skill/web-stylebook-design/ into a Codex skill location such as .agents/skills/web-stylebook-design/ in your repo, or ~/.agents/skills/web-stylebook-design/ for your user profile.
• If you do not want to install the skill, copy skill/AGENTS.md into your project's AGENTS.md.

Claude Code and other agents

• Point your agent's skills directory at skill/web-stylebook-design/, or
• Copy skill/CLAUDE.md into your project's CLAUDE.md or equivalent rules file.

Privacy & security

| Property | | |----------|---| | API key | None | | Model calls | None | | Network access | None — works fully offline | | Project filesystem access | None — the server only reads its bundled catalog snapshot | | Behavior | Deterministic, read-only |

The server reads from a catalog snapshot bundled in the package. Nothing is sent anywhere; the same inputs always yield the same contracts.

Catalog source sync

The canonical catalog is authored in the web-stylebook repository. After generating its local MCP handoff snapshot, verify byte-for-byte parity before releasing this package:

npm run catalog:check-canonical -- /absolute/path/to/web-stylebook/packages/mcp/generated

Without an argument, the command uses WEB_STYLEBOOK_CANONICAL_CATALOG_DIR or the local sibling path ../showcase/packages/mcp/generated. The regular test suite verifies the bundled artifact's internal hash, enums, counts, and runtime contract; this command is the explicit cross-repository source check.

Compatibility

• Node: ≥ 20
• Transport: stdio (Model Context Protocol)
• Clients: Codex CLI / IDE extension, Claude Code, Claude Desktop, Cursor, Windsurf, and any MCP-compatible client

License

MIT — covers the code and the bundled catalog snapshot (free for commercial use).

The webstylebook.com website is licensed CC BY-NC. The same owner grants an MIT license for the catalog snapshot bundled in this package.

UX-principle entries are independently written application and verification guidance. They attribute and link to Laws of UX (CC BY-NC-ND 4.0) and supporting references; Laws of UX prose, illustrations, and page layouts are not bundled.

Interface-design-principle entries form an independently authored, task-oriented review system for contemporary interfaces. They cover semantic structure, responsive reflow, localization, tokens and themes, multiple input modes, complete state models, recovery, and motion preferences.