Content
# Design Systems MCP Server
An AI-powered Model Context Protocol (MCP) server providing intelligent access to authoritative design systems knowledge. 395 curated entries spanning W3C standards, WCAG guidelines, design system practice, and — the part a general-purpose model cannot help you with — the 2025-2026 agent-interface protocols.
🌐 **Live Demo:** [https://design-systems-mcp.southleft.com/](https://design-systems-mcp.southleft.com/)
## Why this exists
A frontier model already knows Atomic Design, BEM, and the WCAG success criteria. It does not reliably know that MCP Apps moved from `_meta["openai/outputTemplate"]` to `_meta.ui.resourceUri`, or that A2UI reached v1.0 candidate in June 2026. On fast-moving specs, **every model's training is stale in a way it cannot detect** — it answers confidently with last year's field names.
That is what this server is for: dated, cited, extracted primary-source content that beats both a smaller model's guess and a frontier model's expensive live re-research.
## Features
### Core Capabilities
- 🎯 **Vector + Keyword Search** - Supabase pgvector with pluggable embeddings (Cloudflare Workers AI `bge-m3`, edge-native and free within the Workers plan; OpenAI optional), plus a Postgres full-text path that keeps working when embeddings are unavailable
- 📚 **395 Curated Entries** - W3C standards, WCAG 2.2, ARIA practices, major design systems, and agent-interface protocols
- 🚦 **Relevance Floor** - IDF-weighted scoring means an uncovered topic returns *nothing* rather than confident, adjacent content
- 🚀 **Edge-Optimized** - Cloudflare Workers deployment with global distribution
### Latest Updates
- 🤖 **Agent-Interface Coverage (Aug 2026)** - A2UI v1.0, MCP Apps SEP-1865, AG-UI, Sentient Design, generative/ephemeral UI, component contracts
- 🧪 **Eval Harness** - `scripts/eval-mcp.ts` scores retrieval *and* substance across four difficulty tiers
- 🛡️ **Source Reliability Badges** - Every answer flags Primary / Authoritative / Reference / Example / Community sources
- 📖 **Universal MCP Client Support** - Works with any MCP-capable client (Claude Desktop, Cursor, Windsurf, Codex, etc.)
- 🏛️ **Major Design Systems, Deeply** - Carbon, Polaris, Atlassian, Material 3, Fluent, Spectrum, Nord, Mantine, shadcn/ui, Radix, Untitled UI — the guidance and token architecture, not just prop tables
### Developer Experience
- 🌐 **Zero Setup Required** - Public MCP endpoint ready to use
- 🤖 **AI Chat Interface** - Natural-language Q&A grounded in the knowledge base, streamed via Cloudflare Workers AI (Llama 3.3 70B) — no OpenAI, no API credits
- 🧪 **Local Development** - Complete testing environment with hot reload
- 📝 **Comprehensive Docs** - Updated setup guides for every major MCP client
## Content Library
### 395 Curated Entries Including:
**Agent Interfaces & AI (2025-2026 — the material a general model gets wrong)**
- A2UI Protocol v1.0 (Google) — adjacency-list components, catalog negotiation, A2A binding
- MCP Apps / SEP-1865 — `ui://` resources, CSP metadata, the `ui/` method namespace, host theming variables
- AG-UI event reference; OpenAI Apps SDK → MCP Apps field-level migration map
- Sentient Design (Josh Clark) — the framework, the triangle, radically adaptive experiences
- Generative & ephemeral UI — Google Research's generative UI paper, content-vs-chrome
- Component contracts and components-as-data (Nathan Curtis, Christine Vallaure)
- AGENTS.md / SKILL.md / DESIGN.md — the agent-facing design system layer
- How Lovable, v0, Figma Make, and Replit each ingest a design system
- The source-of-truth debate: three camps, and why "code-led vs design-led" isn't the real vocabulary
- Context-Based Design Systems, component contracts, and machine-readable documentation
- How a design system reaches Claude Code, Copilot, Cursor, and Windsurf
**Standards & Specifications**
- W3C Design Tokens Community Group (DTCG) Specification
- WCAG 2.2 Guidelines (A, AA, AAA levels)
- WAI-ARIA Authoring Practices Guide (APG)
- W3C Web Content Accessibility Guidelines
- W3C Mobile Accessibility at W3C
**Design System Resources**
- Material Design 3 (Google)
- Fluent Design System (Microsoft)
- Ant Design (Alibaba)
- Carbon Design System (IBM)
- Polaris (Shopify)
- Lightning Design System (Salesforce)
- Atlassian Design System
- Adobe Spectrum
- GitHub Primer
- Shopify Polaris
**Tools & Frameworks**
- Figma Design System Guides
- Style Dictionary Documentation
- Design Tokens Format Module
- Storybook Best Practices
**Methodologies & Best Practices**
- Atomic Design principles
- Design Systems Handbook
- Component architecture patterns
- Accessibility implementation guides
## Quick Start
### Using the Public MCP Server (Recommended)
No installation needed! Connect any MCP client to our live server:
```
https://design-systems-mcp.southleft.com/mcp
```
See [Connect to MCP Clients](#connect-to-mcp-clients) section below for detailed setup instructions.
### Local Development
1. **Clone and Install**
```bash
git clone https://github.com/southleft/design-systems-mcp.git
cd design-systems-mcp
npm install
```
2. **Configure Environment**
```bash
cp .dev.vars.example .dev.vars
# Edit .dev.vars and add your credentials
```
3. **Start Development Server**
```bash
npm run dev
```
Server available at: `http://localhost:8787`
## Connect to MCP Clients
Choose your AI coding tool below for setup instructions:
<details>
<summary><b>Claude Desktop</b> - Click to expand configuration</summary>
**Add via Custom Connector UI (Recommended - No JSON editing!)**
1. **Open Claude Desktop** and navigate to **Settings** → **Connectors**
2. **Click "Add custom connector"** at the bottom of the connectors list
3. **Fill in the connector details:**
- **Name**: `Design Systems Assistant` (or any name you prefer)
- **URL**: `https://design-systems-mcp.southleft.com/mcp`
4. **Click "Add"** to save the connector
5. **Start using it!** The connector will appear in your connectors list with 4 available tools:
- `search_design_knowledge`
- `search_chunks`
- `browse_by_category`
- `get_all_tags`
- `browse_by_tag`
**That's it!** You can now use the Design Systems Assistant in your Claude Desktop conversations.
**Note:** Custom connectors are available for Claude Pro, Team, and Enterprise plans.
</details>
<details>
<summary><b>Claude Code (CLI)</b> - Click to expand configuration</summary>
**Quick Setup via CLI:**
```bash
claude mcp add --transport http design-systems https://design-systems-mcp.southleft.com/mcp
```
**Or manually edit `.mcp.json`:**
```json
{
"mcpServers": {
"design-systems": {
"type": "http",
"url": "https://design-systems-mcp.southleft.com/mcp"
}
}
}
```
**Verify connection:**
```bash
claude mcp list
```
</details>
<details>
<summary><b>Cursor IDE</b> - Click to expand configuration</summary>
**Location:** `~/.cursor/mcp_config.json` or `~/.config/cursor/mcp_config.json`
```json
{
"mcpServers": {
"design-systems": {
"url": "https://design-systems-mcp.southleft.com/mcp"
}
}
}
```
**Restart Cursor** after updating the configuration.
</details>
<details>
<summary><b>Cline (VSCode Extension)</b> - Click to expand configuration</summary>
**Location:** VSCode Settings → Extensions → Cline → MCP Settings
**Add to MCP servers configuration:**
```json
{
"design-systems": {
"url": "https://design-systems-mcp.southleft.com/mcp",
"description": "Design systems knowledge and best practices"
}
}
```
**Or add via Command Palette:** `Cline: Add MCP Server`
**Reload VSCode** after configuration.
</details>
<details>
<summary><b>Continue (VSCode Extension)</b> - Click to expand configuration</summary>
**Location:** VSCode Settings → Extensions → Continue → config.json
```json
{
"mcpServers": [
{
"name": "design-systems",
"url": "https://design-systems-mcp.southleft.com/mcp",
"description": "Design systems knowledge base"
}
]
}
```
</details>
<details>
<summary><b>Zed Editor</b> - Click to expand configuration</summary>
**Location:** `~/.config/zed/settings.json`
```json
{
"mcp": {
"servers": {
"design-systems": {
"url": "https://design-systems-mcp.southleft.com/mcp"
}
}
}
}
```
</details>
<details>
<summary><b>Generic MCP Client</b> - Click to expand configuration</summary>
For any MCP client supporting remote servers:
**Endpoint:** `https://design-systems-mcp.southleft.com/mcp`
**Protocol:** JSON-RPC 2.0 over HTTP/HTTPS
**Transport:** Standard MCP transport (stdio, SSE, or HTTP)
</details>
<details>
<summary><b>Local Development Setup</b> - Click to expand configuration</summary>
To connect to your local development server instead of the public endpoint:
```json
{
"mcpServers": {
"design-systems": {
"url": "http://localhost:8787/mcp"
}
}
}
```
**Note:** Local server requires running `npm run dev` first.
</details>
### Connection Troubleshooting
**Server not responding?**
- Verify the URL is correct: `https://design-systems-mcp.southleft.com/mcp`
- Test with curl: `curl https://design-systems-mcp.southleft.com/health`
- Check your client supports remote MCP servers
**Tools not appearing?**
- Restart your MCP client after configuration changes
- Check client logs for connection errors
- Verify JSON configuration syntax is correct
**Need help?**
- Open an issue: [GitHub Issues](../../issues)
## Available MCP Tools
The server provides these tools for AI assistants:
### search_design_knowledge
Search the complete knowledge base with semantic understanding.
**Parameters:**
- `query` (string, required) - Search query
- `category` (string, optional) - Filter by category
- `tags` (array, optional) - Filter by tags
- `limit` (number, optional) - Max results (default: 15)
**Example:**
```json
{
"name": "search_design_knowledge",
"arguments": {
"query": "WCAG 2.2 color contrast requirements",
"category": "guidelines",
"limit": 5
}
}
```
### search_chunks
Find specific information within content chunks for detailed answers.
**Parameters:**
- `query` (string, required) - Search query
- `limit` (number, optional) - Max chunks (default: 8)
**Example:**
```json
{
"name": "search_chunks",
"arguments": {
"query": "W3C DTCG design tokens specification",
"limit": 3
}
}
```
### browse_by_category
Browse content organized by category.
**Categories:** components, tokens, patterns, guidelines, workflows, general
**Parameters:**
- `category` (string, required) - Category to browse
### get_all_tags
Get all available content tags for filtering and exploration.
## API Examples
### Direct API Testing
**Health Check:**
```bash
curl https://design-systems-mcp.southleft.com/health
```
**MCP Tools List:**
```bash
curl -X POST https://design-systems-mcp.southleft.com/mcp \
-H "Content-Type: application/json" \
-d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'
```
**Search Query:**
```bash
curl -X POST https://design-systems-mcp.southleft.com/mcp \
-H "Content-Type: application/json" \
-d '{
"jsonrpc": "2.0",
"id": 2,
"method": "tools/call",
"params": {
"name": "search_chunks",
"arguments": {"query": "design tokens", "limit": 3}
}
}'
```
**AI Chat Interface (streaming):**
The `/ai-chat` endpoint returns a **Server-Sent Events** stream so content appears progressively. Each event is `data: {"t": "<chunk>"}\n\n`, terminated by `event: done\ndata: {}\n\n`.
```bash
curl -N -X POST https://design-systems-mcp.southleft.com/ai-chat \
-H "Content-Type: application/json" \
-d '{"message":"What are the WCAG 2.2 contrast requirements?"}'
```
The hosted web UI at `/` consumes this stream and renders markdown progressively.
## Adding Content
### Ingest Web Content
```bash
# Single URL
npm run ingest:url https://material.io/components/buttons
# Bulk from CSV
npm run ingest:csv urls.csv
# Crawl entire website
npm run crawl:website https://polaris.shopify.com --max-depth 3
```
### Ingest PDF Content
```bash
npm run ingest:pdf path/to/design-guide.pdf
```
### Generate Vector Embeddings
```bash
npm run ingest:vectors
```
## Development
### Available Scripts
- `npm run dev` - Start local development server
- `npm run deploy` - Deploy to Cloudflare Workers
- `npm run ingest:pdf <file>` - Ingest PDF content
- `npm run ingest:url <url>` - Ingest web content
- `npm run ingest:csv <file>` - Bulk ingest from CSV
- `npm run crawl:website <url>` - Crawl entire websites
- `npm run ingest:vectors` - Generate embeddings for all content
- `npm run setup:supabase` - Initialize Supabase database
- `npm run check:duplicates` - Check for duplicate content
### Project Structure
```
design-systems-mcp/
├── src/
│ ├── index.ts # Main MCP server, transports, tool dispatch, embedded chat UI
│ ├── sse-session.ts # SSE transport (Durable Object)
│ ├── streamable-http-handler.ts # Streamable HTTP transport (/mcp)
│ ├── oauth-handler.ts # OAuth flow
│ └── lib/
│ ├── content-manager.ts # Content management
│ ├── search-handler.ts # Vector + keyword search dispatch
│ ├── source-authority.ts # Reliability tiers & APG disclaimers
│ └── ... (chunker, formatters, ingestion helpers)
├── content/
│ └── entries/ # Ingested content (JSON)
├── supabase/
│ └── migrations/ # SQL schema + RPC functions
├── scripts/
│ ├── ingestion/ # Content ingestion pipeline (URL, PDF, HTML, CSV, crawler)
│ └── build/ # Build helpers (manifest generation)
├── types/
│ └── content.ts # TypeScript definitions
├── wrangler.jsonc # Cloudflare Workers config
└── .dev.vars # Local environment variables
```
## Deployment
### Deploy to Cloudflare Workers
1. **Login to Cloudflare**
```bash
npx wrangler login
```
2. **Set Secrets**
```bash
npx wrangler secret put OPENAI_API_KEY
npx wrangler secret put SUPABASE_URL
npx wrangler secret put SUPABASE_SERVICE_KEY
npx wrangler secret put SUPABASE_ANON_KEY
```
3. **Deploy**
```bash
npm run deploy
```
See [DEPLOYMENT.md](DEPLOYMENT.md) for detailed instructions.
## Vector Search Architecture
This server uses Supabase for production-grade vector search:
- **Database:** PostgreSQL with pgvector extension
- **Embeddings:** Cloudflare Workers AI `@cf/baai/bge-m3` (1024-dim, edge-native, no API key) via `VECTOR_SEARCH_PROVIDER=cloudflare`; OpenAI `text-embedding-3-small` (1536-dim) also supported
- **Threshold:** 0.15 for optimal recall
- **Hybrid Search:** Combines semantic vectors with text matching
- **Performance:** Sub-100ms queries with proper indexing
**Statistics:**
- 395 entries in production database
- 4,800+ content chunks; entry-level vector search via Cloudflare Workers AI
- W3C standards, WCAG guidelines, design system documentation
- Regular updates with new authoritative sources
## Troubleshooting
### Common Issues
**Vector search not working:**
- Check Supabase credentials in environment variables
- Verify database tables exist: `npm run setup:supabase`
- Check logs: `npx wrangler tail`
**Content not found:**
- Verify content exists: `npm run check:duplicates`
- Check if embeddings generated: Look for `embedding` field in content entries
- Test search locally: `npm run dev` and use curl commands
**MCP connection fails:**
- Verify URL is correct and accessible
- Check client supports remote MCP servers
- Test with curl: `curl https://design-systems-mcp.southleft.com/health`
- Restart MCP client after configuration changes
## Documentation
- [DEPLOYMENT.md](DEPLOYMENT.md) - Production deployment
- [CONTRIBUTING.md](CONTRIBUTING.md) - How to contribute and add content
- [CREDITS.md](CREDITS.md) - Content sources and attribution
## License & Attribution
**License:** MIT License - Free for personal and commercial use
**Content Attribution:** This project compiles design systems knowledge from many brilliant creators. All original content remains the intellectual property of their respective authors.
- See [CREDITS.md](CREDITS.md) for complete attribution
- Always link back to original sources when sharing insights
- Support original creators by visiting their websites
## Security & Privacy
- No sensitive data stored - Only public design system knowledge
- Environment variables use Cloudflare secrets
- Open source and auditable
- Privacy-focused - No user data collection
- Regular security updates
Report security issues to: [GitHub Security](../../security/advisories)
## Contributing
We welcome contributions! Whether you want to:
- Report bugs or issues
- Suggest new features
- Add more design system content
- Improve the codebase
- Enhance documentation
Please:
1. Check existing [issues](../../issues)
2. Open a new issue to discuss
3. Submit a pull request
4. Follow [contribution guidelines](CONTRIBUTING.md)
## Support
- Issues: [GitHub Issues](../../issues)
- Discussions: [GitHub Discussions](../../discussions)
- Live Demo: [https://design-systems-mcp.southleft.com/](https://design-systems-mcp.southleft.com/)
## Acknowledgments
Thanks to the design systems community for sharing knowledge:
- Brad Frost for Atomic Design methodology
- W3C Design Tokens Community Group
- Web Accessibility Initiative (WAI)
- All design teams who openly share their work
- The entire design systems community
See [CREDITS.md](CREDITS.md) for the complete list.
---
Built with ❤️ using Cloudflare Workers and the Model Context Protocol
