# CSS First
An advanced MCP (Model Context Protocol) server that provides intelligent, context-aware CSS-first solutions for UI implementation tasks. Features semantic analysis, framework detection, and intelligent ranking with direct MDN integration.
## Setup
Choose between **Remote MCP** (Server-Sent Events) or **Local MCP** (stdio) installation:
### 🌐 Remote MCP via SSE (Recommended)
Connect to our hosted Cloudflare Worker instance - no local installation required:
**URL:** `https://mcp-css-first.chylik-lukas.workers.dev/sse`
#### Claude Desktop
Add to `~/Library/Application Support/Claude/claude_desktop_config.json`:
```json
{
"mcpServers": {
"css-first-remote": {
"url": "https://mcp-css-first.chylik-lukas.workers.dev/sse",
"transport": "sse"
}
}
}
```
#### Cursor / Windsurf / Cline
Add to your MCP settings:
```json
{
"mcpServers": {
"css-first-remote": {
"serverUrl": "https://mcp-css-first.chylik-lukas.workers.dev/mcp"
}
}
}
```
#### Claude Code CLI
Edit `~/.config/claude/config.json` and add:
```json
{
"mcpServers": {
"css-first-remote": {
"url": "https://mcp-css-first.chylik-lukas.workers.dev/sse",
"transport": "sse"
}
}
}
```
---
### 💻 Local MCP via stdio
Install and run locally using npm package:
#### Claude Desktop
Add to `~/Library/Application Support/Claude/claude_desktop_config.json`:
```json
{
"mcpServers": {
"css-first": {
"command": "npx",
"args": ["-y", "@depthark/css-first"]
}
}
}
```
#### Cursor
Add to MCP settings (`.cursor/mcp_settings.json` or via Settings UI):
```json
{
"mcpServers": {
"css-first": {
"command": "npx",
"args": ["-y", "@depthark/css-first"]
}
}
}
```
#### Windsurf
Add to MCP configuration:
```json
{
"mcpServers": {
"css-first": {
"command": "npx",
"args": ["-y", "@depthark/css-first"]
}
}
}
```
#### Cline (VS Code Extension)
Add to Cline MCP settings:
```json
{
"mcpServers": {
"css-first": {
"command": "npx",
"args": ["-y", "@depthark/css-first"]
}
}
}
```
#### Claude Code CLI
```bash
claude mcp add css-first npx -y @depthark/css-first
```
#### Codex
Add to `mcp_servers.toml`:
```toml
[mcp_servers.css-first]
command = "npx"
args = ["-y", "@depthark/css-first"]
```
#### Zed Editor
Add to Zed settings:
```json
{
"context_servers": {
"css-first": {
"command": {
"path": "npx",
"args": ["-y", "@depthark/css-first"]
}
}
}
}
```
---
### 🚀 Deploy Your Own Remote Instance
Deploy your own Cloudflare Worker:
```bash
git clone https://github.com/luko248/css-first
cd css-first
bun install
bun run build:core
bun run deploy:worker
```
Then use your custom URL:
```
https://mcp-css-first.<your-subdomain>.workers.dev/sse
```
## Usage
After adding the configuration:
1. Restart your MCP client
2. Ask CSS questions like:
- "Create a responsive card layout"
- "Center a div vertically and horizontally"
- "Add dark mode support"
- "Make a sticky header"
- "Create organic rounded corners with corner-shape"
- "Design modern buttons with superellipse curves"
## 🚀 Key Features
### **Intelligent Analysis**
- **Semantic Intent Recognition**: Understands user intent through advanced pattern matching (layout, animation, spacing, etc.)
- **Confidence Scoring**: Provides transparency with confidence levels for suggestions
- **Context-Aware Keywords**: Enhanced keyword extraction with semantic understanding
### **Project Context Awareness**
- **Framework Detection**: Automatically detects React, Vue, Angular, Svelte projects
- **CSS Framework Recognition**: Supports Tailwind, Bootstrap, Material-UI, Chakra UI
- **Build Tool Integration**: Recognizes Webpack, Vite, Parcel, Rollup environments
- **Constraint Analysis**: Understands project constraints (performance, accessibility, responsive)
### **Enhanced MDN Integration**
- **Direct MDN Parsing**: Pulls property data straight from MDN pages
- **Performance Caching**: 1-hour intelligent caching for improved response times
- **Real-time Browser Support**: Compatibility data derived from MDN content
### **Intelligent Ranking**
- **Relevance Scoring**: Suggestions ranked by intent match, browser support, and framework compatibility
- **Category-Prioritized Search**: Focuses on most relevant CSS feature categories
- **Framework-Specific Recommendations**: Tailored advice for your tech stack
### **User Experience**
- **Consent-Driven Workflow**: User approval required before property recommendations
- **Detailed Analysis**: Optional semantic analysis breakdown for transparency
- **Implementation Guidance**: Framework-specific best practices and code examples
## Development Installation
For contributors and advanced users who want to modify the source:
```bash
git clone https://github.com/luko248/css-first
cd css-first
bun install
bun run build
```
## Development Usage
For development/testing with local builds:
```json
{
"mcpServers": {
"@depthark/css-first": {
"command": "node",
"args": ["/absolute/path/to/css-first/packages/cli/dist/cli.js"]
}
}
}
```
## Available Tools
### 1. `suggest_css_solution` ⭐
Enhanced CSS-first solution suggester with semantic analysis, context awareness, and intelligent ranking.
**Parameters:**
- `task_description` (string): Description of the UI task or problem to solve
- `preferred_approach` (optional): 'modern', 'compatible', or 'progressive'
- `target_browsers` (optional): Array of target browsers/versions
- `project_context` (optional): Project context (framework, existing CSS patterns, constraints) **NEW**
- `include_analysis` (optional): Include semantic analysis details in response **NEW**
- `baseline` (optional): CSS Baseline availability filter: "Widely Available", "Newly Available", "Limited Availability", "Experimental" (fetched from MDN; falls back to support-level heuristics if unavailable)
- `max_suggestions` (optional): Limit number of suggestions (default 3)
- `response_detail` (optional): "compact" (default) or "full" response fields
- compact returns minimal fields (property, description, support_level, baseline, overall_support, mdn_url)
**Examples:**
**Basic Usage:**
```json
{
"task_description": "I need to center a div horizontally and vertically",
"preferred_approach": "modern"
}
```
**With Project Context:**
```json
{
"task_description": "Create a responsive card layout with hover animations",
"preferred_approach": "modern",
"project_context": "React project using Tailwind CSS, targeting Chrome 90+, performance-critical",
"include_analysis": true
}
```
**With Baseline Filter:**
```json
{
"task_description": "Create a tooltip",
"baseline": "Experimental"
}
```
**Full Response Fields:**
```json
{
"task_description": "Create a tooltip",
"response_detail": "full",
"max_suggestions": 5
}
```
**Response includes:**
- Intelligently ranked CSS suggestions
- Framework-specific recommendations
- Semantic analysis breakdown (optional)
- Confidence scoring and intent detection
- Baseline availability labels with emoji color tags
- Support level derived from MDN browser data
- Compact responses by default to reduce token usage
### 2. `check_css_browser_support`
Checks browser support for specific CSS properties using MDN data.
**Parameters:**
- `css_property` (string): CSS property name to check
- `include_experimental` (optional boolean): Include experimental features
**Example:**
```json
{
"css_property": "flexbox",
"include_experimental": false
}
```
### 3. `get_css_property_details`
Retrieves comprehensive information about a CSS property from MDN documentation.
**Parameters:**
- `css_property` (string): CSS property name to get details for
- `include_examples` (optional boolean): Include code examples
**Example:**
```json
{
"css_property": "grid",
"include_examples": true
}
```
### 4. `confirm_css_property_usage`
Confirms user consent for using a specific CSS property and provides implementation guidance.
**Parameters:**
- `css_property` (string): CSS property name user wants to use
- `user_consent` (boolean): User consent to use this CSS property
- `fallback_needed` (optional boolean): Whether fallback solutions are needed
**Example:**
```json
{
"css_property": "container-queries",
"user_consent": true,
"fallback_needed": true
}
```
## 🧠 How It Works
### **Intelligent Analysis Pipeline**
1. **Semantic Intent Recognition**: Advanced regex patterns analyze task descriptions to understand user intent (layout, animation, spacing, responsive, visual, interaction)
2. **Project Context Analysis**: Detects frameworks, CSS libraries, build tools, and constraints from project context string
3. **MDN Integration**:
- Direct MDN parsing for property details and support data
- Caching: 1-hour intelligent cache for performance
4. **Intelligent Ranking**: Scores suggestions based on:
- Intent match relevance
- Browser support level
- Framework compatibility
- User confidence multiplier
5. **Context-Aware Recommendations**: Provides framework-specific guidance and best practices
6. **User Consent & Implementation**: Consent-driven workflow with detailed implementation guidance
### **Example Analysis Flow**
```
Input: "Create a responsive navigation menu with smooth animations"
↓
Intent Detection: layout + responsive + animation (85% confidence)
↓
Context: React + Tailwind detected
↓
Ranked Suggestions:
1. Flexbox layout (95% support) + CSS transitions
2. CSS Grid (92% support) + transform animations
3. Container queries (75% support) with fallbacks
↓
Framework Recommendations: "Use Tailwind's responsive prefixes", "Consider React transition components"
```
## Development
```bash
# Install dependencies
bun install
# Build all packages
bun run build
# Build specific packages
bun run build:core # @css-first/core
bun run build:cli # @depthark/css-first
# Type check
bun run typecheck
# Lint code
bun run lint
# Deploy to Cloudflare Workers
bun run deploy:worker
# Publish CLI to npm
bun run publish:cli
```
## 📁 Project Structure (Bun Monorepo)
```
packages/
├── core/ # @css-first/core - shared CSS services
│ └── src/
│ ├── index.ts # CSS services entry point
│ ├── types.ts # TypeScript interfaces and enums
│ ├── mdnClient.ts # MDN client and parser
│ ├── suggestions.ts # Semantic analysis and intelligent ranking
│ ├── guidance.ts # Implementation guidance
│ ├── contextAnalyzer.ts # Project context detection
│ └── features/ # Modular CSS feature definitions
│ ├── animation/ # Animation and transition features
│ ├── layout/ # Flexbox, Grid features
│ ├── logical/ # Logical properties
│ ├── responsive/ # Responsive design
│ ├── visual/ # Visual effects
│ └── ... # More feature modules
├── cli/ # @depthark/css-first - npm package
│ └── src/
│ └── index.ts # MCP server (stdio/HTTP transport)
└── worker/ # @css-first/worker - Cloudflare Workers
├── src/
│ └── index.ts # McpAgent class for remote MCP (SSE)
└── wrangler.toml # Worker-specific config
```
### **Key Architecture Benefits**
- **Monorepo Structure**: Shared core, separate deployments (npm + Cloudflare)
- **Modular Design**: Each CSS category has dedicated modules for maintainability
- **Semantic Analysis**: Intent recognition and confidence scoring for accuracy
- **Context Awareness**: Framework and project constraint detection
- **Performance Optimized**: Intelligent caching and ranked results
- **Dual Deployment**: Local CLI via npm, remote MCP via Cloudflare Workers
## 🎯 CSS Feature Coverage
### **Intelligent Categories**
The enhanced system provides context-aware suggestions across:
- **Layout** 🏗️: Flexbox, Grid, positioning, display modes
- **Animation** ✨: CSS animations, transitions, transforms
- **Responsive** 📱: Container queries, media queries, viewport units
- **Visual** 🎨: Shadows, gradients, borders, effects
- **Interaction** 🖱️: Hover states, focus, active, disabled
- **Logical Properties** 📐: Writing-mode aware spacing and sizing
- **HTML APIs** 🧩: Dialogs, popovers, invoker commands
- **Typography** 📝: Font properties, text alignment, spacing
- **Positioning** 📍: Static, relative, absolute, fixed, sticky
### **Supported Feature Catalog**
**Logical Spacing**
- Logical Spacing Properties
- Modern CSS Units
**Layout (Flexbox)**
- Flexbox
**Layout (Grid)**
- CSS Grid
- CSS Subgrid
**Animation**
- CSS Transitions
- CSS Animations
- CSS @starting-style
- CSS interpolate-size
- CSS Scroll Timeline
- CSS View Timeline
- CSS Animation Timeline
- CSS Animation Range
- CSS View Timeline Inset
- CSS Timeline Scope
- CSS View Transitions
**Visual**
- CSS Gradients
- CSS Transforms
- Logical Border Properties
- CSS Overflow
- CSS Overflow Clip
- CSS Overscroll Behavior
- CSS Corner Shape
- CSS -webkit-box-reflect
**Responsive**
- Media Queries
**Interaction**
- CSS Scroll Snap
- Modern CSS Carousel with Pseudo-Elements
**Selectors**
- Basic Selectors
- Attribute Selectors
- State Pseudo-classes
- Structural Pseudo-classes
- Modern Selectors
- Pseudo-elements
- Form Validation Selectors
**Logical**
- CSS if() Function
**HTML**
- Invoker Commands
- Dialog closedby Attribute
**Positioning**
- CSS Anchor Positioning
- Anchor Positioning with Container Queries
- Anchor Name
- Position Anchor
- Position Area
- Position Try Properties
- Position Visibility
- Position Try At-Rule
- Anchor Functions
**Display**
- CSS Display Property
- Display Contents
- Flexbox Display
- Grid Display
- Inline Display Values
- Block Display Values
- Table Display Values
- Display None
- List Item Display
- Flow Root Display
- Subgrid Display
**Modern: Container & Queries**
- CSS Container Queries
- CSS Container Style Queries
- CSS Container Scroll State Queries
- CSS Anchor Positioning
- Anchor Positioning with Container Queries
- Expanded Range Syntax
**Modern: Layout & Sizing**
- CSS Subgrid
- CSS Masonry Layout
- CSS Grid Lanes (Masonry)
- CSS Sizing Properties
- Flexbox gap Property
- Enhanced Logical Properties
- Mobile Viewport Heights
- Stretch Sizing Keyword
- CSS aspect-ratio
- CSS Nesting
**Modern: Color & Visual**
- CSS color-mix() Function
- CSS color-contrast() Function
- CSS accent-color
- CSS color-scheme
- CSS light-dark() Function
- Enhanced Light-Dark Theme System
- CSS backdrop-filter
- CSS conic-gradient
- CSS image-set() Function
- Enhanced Text Decoration
- Enhanced font-variant Properties
- Text Box Trim
**Modern: Motion & Transitions**
- Scroll-driven Animations
- Scroll-triggered Animations
- CSS View Transitions
- View Transition Group Property
- Scoped View Transitions
**Modern: Interaction & UI Patterns**
- CSS Carousel with Modern Pseudo-Elements
- Scroll-Driven Carousel Animations
- CSS-Only Form Validation
- CSS-Only Modal/Dialog
- CSS-Only Tabs/Accordion
- CSS-Only Navigation Patterns
- CSS-Only Loading/Skeleton
- Popover API
- Interest Invokers
- Scroll Target Group
**Modern: Media & Environment**
- Enhanced prefers-\* Media Queries
- CSS forced-colors Media Query
- CSS env() Function
- CSS scroll-behavior
- CSS overscroll-behavior
**Modern: Functions & Syntax**
- CSS Enhanced Math Functions
- CSS if() Conditional Function
- CSS Custom Functions (@function)
- CSS shape() Function
- Advanced attr() Function
- Tree Counting Functions
- Customizable Select Element
### **Framework-Specific Features**
- **React**: Component-scoped styling, CSS-in-JS patterns
- **Vue**: Scoped styles, transition components
- **Angular**: ViewEncapsulation, Material Design integration
- **Svelte**: Built-in scoped styling, reactive CSS
### **CSS Framework Integration**
- **Tailwind**: Utility-first patterns, responsive prefixes
- **Bootstrap**: Grid system, utility classes
- **Material-UI**: Theme customization, sx props
- **Chakra UI**: Design system tokens
## 📊 Enhanced Browser Support Levels
- **Excellent** (95%+): ✅ Safe for production use
- **Good** (85%+): ⚠️ Consider fallbacks for legacy browsers
- **Moderate** (70%+): ⚡ Use with caution and provide fallbacks
- **Limited** (<70%): 🔄 Consider alternative approaches
- **Experimental** (varies): 🧪 Cutting-edge features with progressive enhancement
## ✅ CSS Baseline Availability
Baseline labels are fetched from MDN and kept current; if MDN doesn't expose a Baseline status for a property, the server falls back to the support-level heuristic.
When you pass the `baseline` parameter, responses include an emoji tag per suggestion:
- **🟢 Widely Available**: broadly supported and safe for most production usage
- **🔵 Newly Available**: recently supported, validate target browsers
- **🟡 Limited Availability**: spotty support; use progressive enhancement
- **🟣 Experimental**: likely behind flags or drafts; only for experiments
## 🔧 Automated Feature Discovery
This MCP features **automated CSS feature discovery** using MDN documentation. The system continuously discovers and integrates recent CSS features (2021-2025) with intelligent categorization.
### **Automated Feature Discovery**
- **🤖 Auto-Discovery**: Automatically finds and categorizes new CSS features from MDN
- **📊 Intelligent Categorization**: Uses semantic analysis to categorize features by type
- **🔄 Continuous Updates**: Built-in mechanisms for ongoing feature maintenance
- **📈 Browser Support Analysis**: Automatic extraction of compatibility information
### **Recently Integrated Features (2021-2025)**
#### **🆕 Major CSS Features Added**
- **Container Queries** (2022): Element-based responsive design with logical units (`cqi`, `cqb`) and style/scroll queries
- **CSS Nesting** (2023): Native CSS nesting without preprocessors
- **:has() Pseudo-class** (2022): Parent selection based on children
- **Dynamic Viewport Units** (2022-2023): Complete logical viewport units (`dvi`, `dvb`, `svi`, `svb`, `lvi`, `lvb`) with physical fallbacks
- **color-mix() Function** (2021-2024): Advanced color mixing in different color spaces
- **Scroll-driven Animations** (2023-2024): Animations driven by scroll progress
- **CSS Cascade Layers** (2022): Better style organization with @layer
- **Subgrid** (2021-2023): Grid items participating in parent grid
- **aspect-ratio Property** (2021): Native aspect ratio control
- **Enhanced Math Functions** (2021-2023): clamp(), round(), trigonometric functions
#### **📱 Responsive & Modern Layout**
- **CSS Anchor Positioning** (2024): Position elements relative to other elements
- **View Transitions** (2023-2024): Smooth page/view transitions
- **Enhanced Logical Properties**: Complete writing-mode aware spacing, sizing, and positioning
- **Container Style Queries**: Query container's computed style values
- **Container Scroll State Queries**: Query container's scroll state
- **Masonry Layout** (Experimental): Pinterest-style layouts
#### **🎨 Visual & Color Enhancements**
- **accent-color**: Customize form control colors
- **color-scheme**: Light/dark mode indication
- **light-dark() Function**: Theme-aware color values
- **backdrop-filter**: Glass morphism effects
- **conic-gradient**: Conical gradients for complex designs
- **corner-shape** (Experimental): Superellipse curves for organic, Apple-like rounded corners
### **Automated Update Commands**
```bash
# Discover and integrate new CSS features from MDN
npm run update-features
# Run feature discovery (development)
npm run discover-features
```
### **MDN Setup**
- Uses direct MDN parsing with caching and structured extraction
- No external MCP dependencies required for documentation lookups
## 🌍 Logical Units & Internationalization
This MCP implements a **logical-first approach** to CSS suggestions, prioritizing writing-mode aware properties for better internationalization support.
### **Logical Units Priority System**
#### **Viewport Units (Logical Preferred)**
- `dvi`, `dvb` (dynamic viewport inline/block) → `dvw`, `dvh` (physical fallback)
- `svi`, `svb` (small viewport inline/block) → `svw`, `svh` (physical fallback)
- `lvi`, `lvb` (large viewport inline/block) → `lvw`, `lvh` (physical fallback)
#### **Container Query Units (Logical Preferred)**
- `cqi`, `cqb` (container query inline/block) → `cqw`, `cqh` (physical fallback)
#### **CSS Properties (Logical Preferred)**
- `inline-size`, `block-size` → `width`, `height` (physical fallback)
- `margin-inline`, `margin-block` → `margin-left/right`, `margin-top/bottom`
- `padding-inline`, `padding-block` → `padding-left/right`, `padding-top/bottom`
- `border-inline`, `border-block` → `border-left/right`, `border-top/bottom`
- `inset-inline`, `inset-block` → `left/right`, `top/bottom`
### **Advanced Container Queries**
#### **Size-based Container Queries (Enhanced)**
```css
@container (inline-size > 30cqi) {
.component {
gap: 2cqi;
}
}
```
#### **Style Queries (NEW)**
```css
@container style(--theme: dark) {
.card {
background: var(--dark-bg);
}
}
```
#### **Scroll State Queries (NEW)**
```css
@container scroll-state(stuck: top) {
.header {
backdrop-filter: blur(10px);
}
}
```
### **Writing-Mode Awareness**
- **RTL Language Support**: Logical properties automatically adapt to right-to-left languages
- **Vertical Writing Modes**: Properties work correctly with `writing-mode: vertical-rl`
- **International Compatibility**: Suggestions prioritize globally compatible approaches
## License
MIT
