stitch-bridge
MCP server that gives AI coding agents the ability to design UIs through Google Stitch.
Your agent describes what it wants. Stitch generates production-ready HTML. stitch-bridge handles everything in between.
How it works
Your AI Agent <--> stitch-bridge (MCP) <--> Google Stitch SDK --> HTML / Screenshotsstitch-bridge runs as a local Model Context Protocol server over stdio. Any MCP-compatible client (Claude Code, Cursor, Windsurf, etc.) can connect to it and use 9 tools to create, edit, and manage UI designs, all through natural language prompts.
The Stitch SDK handles the actual generation using Gemini models. stitch-bridge fetches the results (HTML source, base64 screenshots) and returns them directly to the agent, so it can inspect, iterate, or save the output without leaving its workflow.
Quick start
1. Get a Stitch API key
Sign up at stitch.google.com and grab your API key.
2. Add to your MCP client
Add to your MCP config (e.g. .mcp.json, claude_desktop_config.json, or your editor's MCP settings):
{
"mcpServers": {
"stitch-bridge": {
"command": "npx",
"args": ["-y", "stitch-bridge"],
"env": {
"STITCH_API_KEY": "your-api-key"
}
}
}
}Or install globally:
npm install -g stitch-bridgeThen configure with command: "stitch-bridge" instead of using npx.
3. Use it
Ask your agent to design something:
"Create a project and generate a mobile login screen with email and Google sign-in"
The agent will call create_project, then generate_screen, and return the full HTML.
Tools
| Tool | Description | Required params | |------|-------------|-----------------| | list_projects | List all accessible projects | - | | create_project | Create a new project | - | | generate_screen | Generate UI from a text prompt | projectId, prompt | | edit_screen | Edit an existing screen | projectId, screenId, prompt | | generate_variants | Create 1-5 design alternatives | projectId, screenId, prompt | | list_screens | List screens in a project | projectId | | get_screen_html | Get full HTML of a screen | projectId, screenId | | get_screen_image | Get base64 screenshot | projectId, screenId | | build_site | Assemble multi-page site from screens | projectId, routes |
Options
Device types: MOBILE, DESKTOP, TABLET, AGNOSTIC
Models: GEMINI_3_PRO, GEMINI_3_FLASH (default)
Both are optional parameters on generate_screen, edit_screen, and generate_variants.
Output
Every tool returns JSON. The key outputs:
Generated screens return the full HTML source inline: ``json { "projectId": "proj-abc", "screenId": "scr-123", "html": "<!DOCTYPE html><html>..." } ``
Screenshots return base64-encoded images: ``json { "screenId": "scr-123", "base64": "iVBORw0KGgo...", "mimeType": "image/png" } ``
Multi-page sites return HTML per route: ``json { "projectId": "proj-abc", "pages": [ { "route": "/", "screenId": "scr-1", "html": "..." }, { "route": "/about", "screenId": "scr-2", "html": "..." } ] } ``
Configuration
| Environment variable | Description | |---------------------|-------------| | STITCH_API_KEY | Stitch API key (recommended) | | STITCH_ACCESS_TOKEN | Alternative: OAuth access token |
One of the two is required.
Development
npm install
npm run build # Compile TypeScript
npm run dev # Watch mode
npm test # Run tests
npm start # Run the MCP serverRequires Node.js >= 18.
License
MIT
