mcpsystem.design MCP Server

A production-ready MCP (Model Context Protocol) server that exposes design system components and style guides for AI assistants. Deployed on Vercel with SSE transport for remote access.

Live Server: https://www.mcpsystem.design/

Features

• Component Specifications: Access detailed props, types, and descriptions for UI components

• Code Examples: Get ready-to-use Tailwind CSS code snippets for each component

• Style Guide: Retrieve colors, typography, spacing scales, and breakpoints

• Search: Find components by name, description, or category

• SSE Transport: Remote access via Server-Sent Events for web deployment

• Security Hardened: Input validation, rate limiting, and structured logging

Quick Start

1. Install Dependencies

npm install

2. Local Development

Run the Next.js development server:

npm run dev

The MCP SSE endpoint will be available at http://localhost:3000/api/sse

3. Deploy to Vercel

# Install Vercel CLI if not already installed
npm i -g vercel

# Deploy
vercel

Project Structure

├── app/                    # Next.js App Router
│   ├── api/
│   │   └── sse/
│   │       └── route.ts    # MCP SSE transport endpoint
│   ├── patterns/           # Pattern documentation pages
│   ├── docs/               # Documentation pages
│   └── page.tsx            # Landing page
├── lib/
│   ├── design-system/      # Design system data
│   │   ├── index.ts        # Main exports and helpers
│   │   ├── components.ts   # Component definitions
│   │   ├── style-guide.ts  # Colors, typography, spacing
│   │   └── types.ts        # TypeScript types
│   ├── mcp/                # MCP protocol utilities
│   │   ├── schemas.ts      # Zod validation schemas
│   │   ├── errors.ts       # JSON-RPC error codes
│   │   ├── logger.ts       # Structured logging
│   │   └── types.ts        # TypeScript types
│   └── security/           # Security utilities
│       ├── host-validator.ts  # Host header validation
│       └── rate-limiter.ts    # Rate limiting
├── components/             # React components for the website
├── packages/               # Publishable packages
│   └── ui/                 # @mcpsystem/ui Web Components
├── scripts/                # Build and validation scripts
│   ├── validate-css-tokens.ts       # CSS token validation
│   └── validate-component-colors.ts # Component color validation
├── package.json
├── tsconfig.json
├── vercel.json
└── README.md

API Endpoints

Available MCP Tools

Pattern Tools (Tailwind CSS)

Tailwind patterns are copy-paste HTML with class variations for variants, sizes, and states.

Style Guide Tools

Component Tools (@mcpsystem/ui)

@mcpsystem/ui components are Lit-based Web Components you import and use.

Connecting to AI Assistants

Cursor

1. Open Cursor Settings (Cmd+, on macOS or Ctrl+, on Windows/Linux)

2. Search for "MCP" or navigate to Features → MCP Servers

3. Click "Add new MCP server"

4. Configure with:

   • Name: mcpdesignsystem

   • Type: sse

   • URL: https://www.mcpsystem.design/sse

Alternatively, add to your .cursor/mcp.json file:

{
  "mcpServers": {
    "mcpdesignsystem": {
      "url": "https://www.mcpsystem.design/sse"
    }
  }
}

Claude Desktop

Add to your Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json on macOS):

{
  "mcpServers": {
    "mcpdesignsystem": {
      "url": "https://www.mcpsystem.design/sse"
    }
  }
}

Claude Code CLI

Add to your .claude/settings.json:

{
  "mcpServers": {
    "mcpdesignsystem": {
      "url": "https://www.mcpsystem.design/sse"
    }
  }
}

Customizing the Design System

Modifying Components

Edit lib/design-system/components.ts to add or modify components. Each component follows this structure:

{
  name: "ComponentName",
  slug: "component-name",
  description: "Component description",
  category: "Category",
  usageNote: "<!-- Tailwind CSS pattern - copy the HTML/classes below -->",
  tailwind: true,
  specs: {                          // Class variations - which Tailwind classes to swap
    variants: [
      { name: "Primary", classes: "bg-primary text-primary-foreground" },
      { name: "Secondary", classes: "bg-surface-hover text-default" }
    ],
    sizes: [
      { name: "Small", classes: "h-8 px-3 text-xs" },
      { name: "Medium", classes: "h-10 px-4 text-sm" }
    ],
    states: [
      { name: "Disabled", classes: "opacity-70 cursor-not-allowed" }
    ]
  },
  examples: [
    {
      title: "Example Title",
      code: `<div className="...">Example</div>`,
      preview: "preview-id"
    }
  ],
  relatedComponents: ["OtherComponent"]
}

Modifying Style Guide

Update lib/design-system/style-guide.ts:

• Colors: Organized by category (Semantic tokens, Gray Scale, Accent)

• Typography: Font family, size, weight, line-height for each style

• Spacing: Token name, CSS value, and pixel equivalent

• Breakpoints: Responsive breakpoint values and descriptions

Color Token Rules

Component examples must use semantic color tokens instead of raw Tailwind colors:

Validation

The project includes two validation scripts that run automatically on build:

CSS Token Validation

Ensures CSS variables in globals.css match the design tokens in style-guide.ts:

npm run validate:tokens

Component Color Validation

Ensures component examples use semantic color tokens instead of raw Tailwind colors:

npm run validate:component-colors

Run All Validations

npm run validate

Always run npm run validate before committing changes to ensure design system consistency.

Development

Type Checking

npm run typecheck

Validation

npm run validate          # Run all validations (recommended before commits)
npm run validate:tokens   # CSS token validation only
npm run validate:component-colors  # Component color validation only

Building

npm run build             # Runs validation + production build

Security

The SSE endpoint includes several security hardening measures:

Input Validation

• All JSON-RPC requests are validated using Zod schemas

• Tool arguments are type-checked before execution

• Batch requests limited to 100 items maximum

Rate Limiting

• 100 requests per minute per IP address

• Returns HTTP 429 with Retry-After header when exceeded

• In-memory rate limiting (resets on cold starts)

Host Header Validation

• Whitelist-based validation prevents host header injection

• Allowed hosts: www.mcpsystem.design, mcpsystem.design, localhost

• Invalid hosts default to www.mcpsystem.design

Structured Logging

• All requests include unique request IDs (X-Request-Id header)

• JSON-formatted logs for Vercel log aggregation

• Request tracing for debugging and auditing

Troubleshooting

SSE Connection Issues

• Ensure your client supports SSE transport for MCP

• Check that CORS headers are properly configured for your client origin

• Vercel has a 60-second timeout for serverless functions; long-running connections may be terminated

Connection Drops

The SSE endpoint sends periodic ping messages to keep the connection alive. If your client disconnects frequently, check your network configuration or proxy settings.

Rate Limit Errors (HTTP 429)

If you receive a 429 status code, you've exceeded the rate limit (100 requests/minute). Wait for the duration specified in the Retry-After header before retrying.

License

MIT