XC-MCP: Intelligent Xcode MCP Server

Production-grade MCP server for Xcode workflows — optimized for AI agents with accessibility-first iOS automation

XC-MCP makes Xcode and iOS simulator tooling accessible to AI agents through intelligent context engineering. V3.0.0 adds platform-native defer_loading support — Claude's tool search automatically discovers tools on-demand, minimizing baseline context overhead while maintaining full 29-tool functionality.

Why XC-MCP?

The Problem: Token Overflow Breaks MCP Clients

Traditional Xcode CLI wrappers dump massive output that exceeds MCP protocol limits:

• simctl list: 57,000+ tokens (unusable in MCP context)
• Build logs: 135,000+ tokens (catastrophic overflow)
• Screenshot-first automation: 170 tokens per screen, 2000ms latency
• No state memory between operations

The Solution: Progressive Disclosure + Accessibility-First

V3.0.0 Architecture:

Platform-native defer_loading on all 29 tools
├─ Claude's tool search discovers tools automatically
├─ Tools loaded on-demand (minimal baseline overhead)
├─ Accessibility-first workflow (50 tokens, 120ms vs 170 tokens, 2000ms)
└─ Workflow tools for common operations (fresh-install, tap-element)

Token Efficiency Evolution:

Key Improvements (V3.0.0):

• ✅ Platform-native defer_loading - All tools deferred; Claude discovers on-demand
• ✅ Workflow tools - High-level abstractions for common operations
• ✅ Zero baseline overhead - Platform handles tool discovery
• ✅ Accessibility-first automation (3-4x faster, 3-4x cheaper than screenshots)
• ✅ Progressive disclosure (summaries → cache IDs → full details on demand)
• ✅ 60% test coverage with comprehensive error handling

Quick Start

# Install globally
npm install -g xc-mcp

# Or run without installation
npx xc-mcp

MCP Configuration (Claude Desktop):

Add to ~/Library/Application Support/Claude/claude_desktop_config.json:

{
  "mcpServers": {
    "xc-mcp": {
      "command": "npx",
      "args": ["-y", "xc-mcp"]
    }
  }
}

Minimal Mode (for Claude Code and other clients that don't support defer_loading):

{
  "mcpServers": {
    "xc-mcp": {
      "command": "npx",
      "args": ["-y", "xc-mcp", "--mini"]
    }
  }
}

The --mini flag reduces tool descriptions from ~18.7k tokens to ~540 tokens (~97% reduction). Use rtfm for full documentation on-demand.

Build-Only Mode (for build-focused workflows without UI automation):

{
  "mcpServers": {
    "xc-mcp": {
      "command": "npx",
      "args": ["-y", "xc-mcp", "--build-only"]
    }
  }
}

The --build-only flag loads only 11 tools (vs 30): xcodebuild tools, simctl-list, cache, and system tools. Excludes IDB/UI automation and workflow tools. Combine with --mini for maximum reduction: ["--mini", "--build-only"].

Token Optimization Architecture

Progressive Disclosure Pattern

XC-MCP returns concise summaries first, with cache IDs for on-demand detail retrieval:

Example: Simulator List (96% token reduction)

// 1. Get summary (2,000 tokens vs 57,000 raw)
simctl-list({ deviceType: "iPhone" })
// Returns:
{
  cacheId: "sim-abc123",
  summary: { totalDevices: 47, availableDevices: 31, bootedDevices: 1 },
  quickAccess: { bootedDevices: [...], recentlyUsed: [...] }
}

// 2. Get full details only if needed
simctl-get-details({
  cacheId: "sim-abc123",
  detailType: "available-only",
  maxDevices: 10
})

Example: Build Operations

// 1. Build returns summary + buildId
xcodebuild-build({ projectPath: "./MyApp.xcworkspace", scheme: "MyApp" })
// Returns:
{
  buildId: "build-xyz789",
  success: true,
  summary: { duration: 7075, errorCount: 0, warningCount: 1 }
}

// 2. Access full logs only when debugging
xcodebuild-get-details({ buildId: "build-xyz789", detailType: "full-log" })

RTFM On-Demand Documentation

Discovery Workflow:

// 1. Browse tool categories
rtfm({ categoryName: "build" })
// Returns: List of build tools with brief descriptions

// 2. Get comprehensive docs for specific tool
rtfm({ toolName: "xcodebuild-build" })
// Returns: Full documentation with parameters, examples, related tools

// 3. Execute with consolidated operations
xcodebuild-build({ scheme: "MyApp", configuration: "Debug" })

Why RTFM?

• Tool descriptions: <10 words + "See rtfm for details"
• Full docs retrieved only when needed
• 80% token savings vs traditional verbose MCP servers

Operation Enum Consolidation

Before V2.0: 21 individual tools

simctl-boot, simctl-shutdown, simctl-create, simctl-delete,
simctl-erase, simctl-clone, simctl-rename, simctl-install,
simctl-uninstall, simctl-launch, simctl-terminate...

V2.0: 6 consolidated routers

simctl-device({ operation: "boot" | "shutdown" | "create" | "delete" | "erase" | "clone" | "rename" })
simctl-app({ operation: "install" | "uninstall" | "launch" | "terminate" })
idb-app({ operation: "install" | "uninstall" | "launch" | "terminate" })
cache({ operation: "get-stats" | "get-config" | "set-config" | "clear" })
persistence({ operation: "enable" | "disable" | "status" })
idb-targets({ operation: "list" | "describe" | "connect" | "disconnect" })

Result: 40% token reduction through shared parameter schemas and unified documentation.

Accessibility-First iOS Automation

Our Philosophy

XC-MCP promotes accessibility-first automation because it:

1. Encourages better apps: Developers building accessible UIs benefit all users (screen readers, voice control, assistive technologies)
2. Enables precise AI interaction: Semantic element discovery via accessibility tree vs visual guesswork from screenshots
3. Improves efficiency: 3-4x faster execution, 3-4x cheaper token cost
4. Reduces energy usage: Skip computationally expensive image processing entirely

Objective Performance Data

Accessibility-First Workflow

// 1. ALWAYS assess quality first
accessibility-quality-check({ screenContext: "LoginScreen" })
// Returns:
{
  quality: "rich" | "moderate" | "minimal",
  recommendation: "accessibility-ready" | "consider-screenshot",
  elementCounts: { total: 12, tappable: 8, textFields: 2 }
}

// 2. Decision branch based on quality
if (quality === "rich" || quality === "moderate") {
  // Use accessibility tree (faster, cheaper)
  idb-ui-find-element({ query: "login" })
  // Returns: { centerX: 200, centerY: 400, label: "Login" }

  idb-ui-tap({ x: 200, y: 400 })
  // Precise coordinate-based interaction

} else if (quality === "minimal") {
  // Fall back to screenshot (last resort)
  screenshot({ size: "half", screenName: "LoginScreen" })
  // Visual analysis when accessibility insufficient
}

Why This Matters:

• For Users: Encourages inclusive app development benefiting everyone
• For AI Agents: Precise semantic targeting vs visual pattern matching
• For Efficiency: 50 tokens (accessibility) vs 170 tokens (screenshot)
• For Speed: 120ms (accessibility) vs 2000ms (screenshot)
• For Energy: Skip image encoding/decoding/analysis entirely

Accessibility Tools (3 specialized)

accessibility-quality-check: Rapid assessment without full tree query

• Returns: rich (>3 tappable) | moderate (2-3) | minimal (≤1)
• Use case: Decision point before screenshot vs accessibility
• Cost: ~30 tokens, ~80ms

idb-ui-find-element: Semantic element search by label/identifier

• Returns: Tap-ready coordinates (centerX, centerY) with frame boundaries
• Use case: Find specific button, field, or cell without visual analysis
• Cost: ~40 tokens, ~120ms

idb-ui-describe: Full accessibility tree with progressive disclosure

• Operation all: Summary + uiTreeId for full tree retrieval
• Operation point: Element details at specific coordinates
• Use case: Discover all interactive elements, validate tap coordinates
• Cost: ~50 tokens for summary, ~500 tokens for full tree

Platform defer_loading (V3.0.0 Feature)

How It Works

XC-MCP V3.0 adds the defer_loading: true flag to all 29 tool registrations. Claude's platform-native tool search automatically:

1. Discovers tools on-demand — No custom tool-search implementation needed
2. Loads tools when relevant — Based on conversation context
3. Minimizes baseline overhead — Zero tokens at startup

RTFM: On-Demand Documentation

Use rtfm to get comprehensive documentation for any tool:

// 1. Browse tool categories
rtfm({ categoryName: "build" })
// Returns all build-related tools with descriptions

// 2. Get comprehensive docs for specific tool
rtfm({ toolName: "xcodebuild-build" })
// Returns full documentation with parameters, examples, related tools

// 3. Execute with discovered parameters
xcodebuild-build({ scheme: "MyApp", configuration: "Debug" })

Environment Variable: Disable defer_loading

Default (V3.0.0): All tools have defer_loading enabled

# Platform discovers and loads tools automatically
# Zero baseline token overhead

Disable defer_loading (for debugging/testing):

# Set environment variable to load all tools at startup
export XC_MCP_DEFER_LOADING=false

# All 29 tools loaded immediately (~18.7k tokens)
# Useful for: Testing, debugging, MCP client compatibility

Workflow Tools (New in V3.0.0)

XC-MCP provides 2 high-level workflow tools that combine common operations into single steps:

workflow-tap-element — High-Level Semantic Tap

Combines accessibility quality check + element search + tap into one operation:

workflow-tap-element({
  elementQuery: "Login",
  screenContext: "LoginScreen",
  inputText: "user@example.com",  // optional: type after tap
  verifyResult: true               // optional: screenshot after action
})
// Does:
// 1. Quality check screen accessibility
// 2. Find element by name/label
// 3. Tap coordinates
// 4. Optionally type text
// 5. Optionally take verification screenshot
// Returns: { success: true, tappedElement: {...}, screenshot?: {...} }

Cost: ~90 tokens (vs 130 tokens separately) Latency: ~300ms (vs ~400ms separately) Use case: User login, form submission, navigation flows

workflow-fresh-install — Clean Install Workflow

Performs complete app refresh: shutdown → (erase) → boot → build → install → launch

workflow-fresh-install({
  projectPath: "./MyApp.xcworkspace",
  scheme: "MyApp",
  simulatorUdid: "...",           // optional: auto-detects
  eraseSimulator: true,           // optional: wipe simulator data
  configuration: "Debug",
  launchArguments: ["--resetData"]
})
// Does:
// 1. Shutdown simulator if running
// 2. Erase simulator state (if requested)
// 3. Boot simulator fresh
// 4. Build app
// 5. Install app
// 6. Launch app with arguments
// Returns: { success: true, buildTime: 7000, bootTime: 3000, launchTime: 500 }

Cost: ~200 tokens (vs 300+ tokens separately) Latency: ~20s (vs 25+ seconds separately) Use case: CI/CD pipelines, clean state testing, fresh debugging sessions

Tool Reference

6 Consolidated Router Tools

simctl-device — Simulator lifecycle (7 operations)

• boot, shutdown, create, delete, erase, clone, rename
• Auto-UDID detection, performance tracking, smart defaults

simctl-app — App management (4 operations)

• install, uninstall, launch, terminate
• Bundle ID resolution, launch arguments, environment variables

idb-app — IDB app operations (4 operations)

• install, uninstall, launch, terminate
• Physical device + simulator support via IDB

cache — Cache management (4 operations)

• get-stats, get-config, set-config, clear
• Multi-layer caching (simulator, project, response, build settings)

persistence — Persistence control (3 operations)

• enable, disable, status
• File-based cache across server restarts

idb-targets — Target management (2 operations)

• list, describe, connect, disconnect
• Physical device and simulator discovery

22 Individual Specialized Tools

Build & Test (6 tools)

• xcodebuild-build: Build with progressive disclosure via buildId
• xcodebuild-test: Test with filtering, test plans, cache IDs
• xcodebuild-clean: Clean build artifacts
• xcodebuild-list: List targets/schemes with smart caching
• xcodebuild-version: Get Xcode and SDK versions
• xcodebuild-get-details: Access cached build/test logs

UI Automation (6 tools)

• idb-ui-describe: Accessibility tree queries (all | point operations)
• idb-ui-tap: Coordinate-based tapping with percentage conversion
• idb-ui-input: Text input with keyboard control
• idb-ui-gesture: Swipes, pinches, rotations with coordinate transforms
• idb-ui-find-element: Semantic element search (NEW in v2.0)
• accessibility-quality-check: Rapid UI richness assessment (NEW in v2.0)

I/O & Media (2 tools)

• simctl-io: Screenshots and video recording with semantic naming
• screenshot: Vision-optimized base64 screenshots (inline, max 800px)

Discovery & Health (3 tools)

• simctl-list: Progressive disclosure simulator listing (96% token reduction)
• simctl-get-details: On-demand full simulator data retrieval
• simctl-health-check: Xcode environment validation

Utilities (5 tools)

• simctl-openurl: Open URLs and deep links
• simctl-get-app-container: Get app container paths (bundle, data, group)
• simctl-push: Simulate push notifications
• rtfm: On-demand comprehensive documentation

Workflow Tools (2 high-level abstractions) - NEW in V3.0.0

• workflow-tap-element: High-level semantic tap (find + tap in one call)
• workflow-fresh-install: Clean install workflow (shutdown → erase → boot → build → install → launch)

Total: 29 active tools (27 core + 2 workflow abstractions)

Usage Examples

Example 1: Accessibility-First Login Automation

// 1. Quality check before choosing approach
accessibility-quality-check({ screenContext: "LoginScreen" })
// → { quality: "rich", tappableElements: 12, textFields: 2 }

// 2. Find email field semantically
idb-ui-find-element({ query: "email" })
// → { centerX: 200, centerY: 150, label: "Email", type: "TextField" }

// 3. Tap and input email
idb-ui-tap({ x: 200, y: 150 })
idb-ui-input({ operation: "text", text: "user@example.com" })

// 4. Find and tap login button
idb-ui-find-element({ query: "login" })
// → { centerX: 200, centerY: 400, label: "Login", type: "Button" }
idb-ui-tap({ x: 200, y: 400 })

// 5. Verify (screenshot only for confirmation, not primary interaction)
screenshot({ screenName: "HomeScreen", state: "LoggedIn" })

Efficiency Comparison:

• Accessibility approach: 4 queries × 50 tokens = 200 tokens, ~500ms total
• Screenshot approach: 3 screenshots × 170 tokens = 510 tokens, ~6000ms total
• Savings: 2.5x cheaper, 12x faster

Example 2: RTFM Discovery Workflow

// 1. Browse tool categories
rtfm({ categoryName: "build" })
// Returns:
{
  category: "build",
  tools: [
    { name: "xcodebuild-build", description: "Build Xcode projects with smart defaults" },
    { name: "xcodebuild-test", description: "Run tests with filtering and test plans" },
    ...
  ]
}

// 2. Get comprehensive docs for specific tool
rtfm({ toolName: "xcodebuild-build" })
// Returns:
{
  tool: "xcodebuild-build",
  description: "Full comprehensive documentation...",
  parameters: { projectPath: "...", scheme: "...", configuration: "..." },
  examples: [...],
  relatedTools: ["xcodebuild-clean", "xcodebuild-get-details"]
}

// 3. Execute with discovered parameters
xcodebuild-build({
  projectPath: "./MyApp.xcworkspace",
  scheme: "MyApp",
  configuration: "Debug"
})

Example 3: Progressive Disclosure Build Workflow

// 1. Build returns summary + buildId
xcodebuild-build({
  projectPath: "./MyApp.xcworkspace",
  scheme: "MyApp"
})
// Returns:
{
  buildId: "build-abc123",
  success: true,
  summary: {
    duration: 7075,
    errorCount: 0,
    warningCount: 1,
    configuration: "Debug",
    sdk: "iphonesimulator"
  },
  nextSteps: [
    "Build completed successfully",
    "Use 'xcodebuild-get-details' with buildId for full logs"
  ]
}

// 2. Access full logs only when debugging
xcodebuild-get-details({
  buildId: "build-abc123",
  detailType: "full-log",
  maxLines: 100
})
// Returns: Full compiler output, warnings, errors

CLAUDE.md Template for End Users

Copy this into your project's CLAUDE.md to guide AI agents toward optimal XC-MCP usage:

# XC-MCP Optimal Usage Patterns

This project uses XC-MCP for iOS development automation. Follow these patterns for maximum efficiency.

## Tool Discovery

1. **Browse categories**: `rtfm({ categoryName: "build" })` — See all build-related tools
2. **Get tool docs**: `rtfm({ toolName: "xcodebuild-build" })` — Comprehensive documentation
3. **Execute**: Use discovered parameters and operations

## Accessibility-First Automation (MANDATORY)

**ALWAYS assess accessibility quality before taking screenshots:**

1. **Check quality**: `accessibility-quality-check({ screenContext: "LoginScreen" })`
   - Returns: `rich` | `moderate` | `minimal`

2. **Decision branch**:
   - IF `rich` or `moderate`: Use `idb-ui-find-element` + `idb-ui-tap` (faster, cheaper)
   - IF `minimal`: Fall back to `screenshot` (last resort)

3. **Why this matters**:
   - Accessibility: 50 tokens, 120ms per query
   - Screenshots: 170 tokens, 2000ms per capture
   - **3-4x cheaper, 16x faster when accessibility sufficient**
   - **Promotes inclusive app development**

## Progressive Disclosure

- Build/test tools return `buildId` or cache IDs
- Use `xcodebuild-get-details` or `simctl-get-details` to drill down
- **Never request full logs upfront** — get summaries first

## Best Practices

- **Let UDID auto-detect** — Don't prompt user for simulator UDIDs
- **Use semantic context** — Include `screenContext`, `appName`, `screenName` parameters
- **Prefer accessibility over screenshots** — Better for efficiency AND app quality
- **Use operation enums** — `simctl-device({ operation: "boot" })` instead of separate tools

## Example: Optimal Login Flow

\`\`\`typescript
// 1. Quality check (30 tokens, 80ms)
accessibility-quality-check({ screenContext: "LoginScreen" })

// 2. IF rich: Semantic search (40 tokens, 120ms)
idb-ui-find-element({ query: "email" })
idb-ui-tap({ x: 200, y: 150 })
idb-ui-input({ operation: "text", text: "user@example.com" })

idb-ui-find-element({ query: "login" })
idb-ui-tap({ x: 200, y: 400 })

// 3. Verify with screenshot only at end (170 tokens, 2000ms)
screenshot({ screenName: "HomeScreen", state: "LoggedIn" })

// Total: ~280 tokens, ~2400ms
// vs Screenshot-first: ~510 tokens, ~6000ms (2.5x slower, 1.8x more expensive)
\`\`\`

Installation & Configuration

Prerequisites

• macOS with Xcode command-line tools
• Node.js 18+
• Xcode 15+ recommended

Install Xcode CLI tools:

xcode-select --install

Installation Options

# Global install (recommended for MCP)
npm install -g xc-mcp

# Or run directly without installation
npx -y xc-mcp

# Local development
git clone https://github.com/conorluddy/xc-mcp.git
cd xc-mcp && npm install && npm run build

MCP Client Configuration

Claude Desktop (~/Library/Application Support/Claude/claude_desktop_config.json):

{
  "mcpServers": {
    "xc-mcp": {
      "command": "npx",
      "args": ["-y", "xc-mcp"],
      "cwd": "/path/to/your/ios/project"
    }
  }
}

Environment Variables (optional):

• XCODE_CLI_MCP_TIMEOUT: Operation timeout in seconds (default: 300)
• XCODE_CLI_MCP_LOG_LEVEL: Logging verbosity (debug | info | warn | error)
• XCODE_CLI_MCP_CACHE_DIR: Custom cache directory path
• XC_MCP_DEFER_LOADING: Enable deferred tool loading (default: true for V3.0)

Breaking Changes & Migration Guide

V3.0.0: Platform defer_loading Support

What Changed:

• All 29 tools now have defer_loading: true flag
• Claude's platform tool search discovers tools automatically
• No custom tool-search implementation needed
• Tools loaded on-demand based on conversation context

Migration Path:

Usage (same as V2.x):

// V3.0 - Platform discovers tools automatically
// Just use tools as before - Claude's tool search handles discovery
xcodebuild-build({ scheme: "MyApp" })

// Use RTFM for documentation discovery
rtfm({ categoryName: "build" })
rtfm({ toolName: "xcodebuild-build" })

// Disable defer_loading for debugging
export XC_MCP_DEFER_LOADING=false

Token Impact:

Development

Build Commands

npm run build          # Compile TypeScript to JavaScript
npm run dev            # Development mode with watch compilation
npm test               # Run Jest test suite (60% coverage)
npm run test:coverage  # Generate coverage report
npm run lint           # ESLint with auto-fix
npm run format         # Prettier code formatting

Testing

• Jest with ESM support and TypeScript compilation
• 60% coverage across statements, branches, functions, lines
• 1136 tests covering core functionality, edge cases, error handling
• Pre-commit hooks enforce code quality via Husky + lint-staged

Architecture

Core Components:

• src/index.ts — MCP server with tool registration and routing
• src/tools/ — 29 tools organized by category (xcodebuild, simctl, idb, cache, workflows)
• src/state/ — Multi-layer intelligent caching (simulator, project, response, build settings)
• src/utils/ — Shared utilities (command execution, validation, error formatting)
• src/types/ — TypeScript definitions for Xcode data structures

Cache Architecture:

• Simulator Cache: 1-hour retention, usage tracking, performance metrics
• Project Cache: Remembers successful build configurations per project
• Build Settings Cache: Auto-discovers bundle IDs, deployment targets, capabilities
• Response Cache: 30-minute retention for progressive disclosure

Contributing

Contributions welcome! Please ensure:

• Tests pass (npm test)
• Coverage remains ≥60% (npm run test:coverage)
• Code passes linting (npm run lint)
• TypeScript compiles (npm run build)

See CLAUDE.md for detailed development guidelines and architecture documentation.

License

MIT License — See LICENSE for details.

XC-MCP: Production-grade Xcode automation for AI agents through progressive disclosure and accessibility-first workflows.