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CUA MCP Server

by taskcrew
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TypeScript
Remote

CUA MCP Server

An agentic Model Context Protocol (MCP) server for CUA Cloud - delegate desktop automation tasks to an autonomous vision-based agent. Images never leave the server; only text summaries are returned.

Production URL: https://cua-mcp-server.vercel.app/mcp

What is CUA?

CUA (Computer Use Agent) provides cloud-based virtual machine sandboxes that AI agents can control. This MCP server exposes CUA's capabilities through a clean task-delegation API:

  • Create and manage VMs (Linux, Windows, macOS)

  • Delegate tasks - "Open Chrome and navigate to google.com"

  • Get text summaries - No images in your context window

  • Query screen state - Vision-based descriptions without taking action

Architecture

Claude Code (Orchestrator) │ │ run_task("Open Chrome and go to google.com") ▼ ┌─────────────────────────────────────────────────────────────┐ │ CUA MCP Server (Agentic) │ │ ┌───────────────────────────────────────────────────────┐ │ │ │ Internal Agent Loop │ │ │ │ 1. screenshot() → CUA sandbox │ │ │ │ 2. screenshot → Claude API (computer_use tool) │ │ │ │ 3. Claude returns: click(x,y) / type("text") / done │ │ │ │ 4. Execute action on sandbox │ │ │ │ 5. Loop until complete │ │ │ └───────────────────────────────────────────────────────┘ │ └─────────────────────────────────────────────────────────────┘ │ ▼ { success: true, summary: "Opened Chrome...", steps_taken: 5 } (TEXT ONLY - no images)

Project Structure

api/mcp.ts # MCP protocol handler lib/ ├── agent/ # Modular agent architecture │ ├── index.ts # Public exports │ ├── types.ts # Type definitions │ ├── config.ts # Model configurations │ ├── validation.ts # Coordinate validation helpers │ ├── execute.ts # Main agent loop │ ├── describe.ts # Screen description │ ├── progress.ts # Progress tracking │ ├── utils.ts # Utilities (sleep, generateTaskId) │ └── actions/ # Action handler registry (16 handlers) ├── cua-client.ts # CUA Cloud API client └── tool-schemas.ts # MCP tool definitions

Available Tools (9 total)

Sandbox Management (5 tools)

Tool

Description

list_sandboxes

List all CUA cloud sandboxes with their current status

get_sandbox

Get details of a specific sandbox including API URLs

start_sandbox

Start a stopped sandbox

stop_sandbox

Stop a running sandbox

restart_sandbox

Restart a sandbox

Note: Create and delete sandboxes via the CUA Dashboard - the Cloud API doesn't expose these operations.

Agentic Tools (4 tools)

Tool

Description

describe_screen

Get a text description of current screen state using vision AI. No actions taken.

run_task

Execute a computer task autonomously. Returns immediately with task_id for polling.

get_task_progress

Poll progress of running tasks. Returns current step, last action, and reasoning.

get_task_history

Retrieve results of a previously executed task by ID.

Quick Start

1. Get a CUA API Key

  1. Go to cua.ai/signin

  2. Navigate to Dashboard > API Keys > New API Key

  3. Copy your API key (starts with sk_cua-api01_...)

2. Configure Claude Code

Add to your ~/.claude.json:

{ "mcpServers": { "cua": { "command": "npx", "args": ["-y", "mcp-remote", "https://cua-mcp-server.vercel.app/mcp"] } } }

3. Use with Claude Code

You: "List my CUA sandboxes" Claude: [Uses list_sandboxes tool] You: "Start my-sandbox" Claude: [Uses start_sandbox tool] You: "Open Firefox and go to google.com on my-sandbox" Claude: [Uses run_task with task="Open Firefox and navigate to google.com"] → Returns: { success: true, summary: "Opened Firefox, navigated to google.com", steps_taken: 4 } You: "What's currently on the screen?" Claude: [Uses describe_screen tool] → Returns: { description: "Firefox browser showing Google homepage with search box..." }

Usage Examples

Automate a Web Task

You: "On my-sandbox, open Chrome, go to github.com, and search for 'mcp server'" Claude uses run_task: - task: "Open Chrome browser, navigate to github.com, find the search box, type 'mcp server' and press Enter" - Returns summary of what happened (no screenshots in your context)

Check Screen State

You: "What's on the screen right now?" Claude uses describe_screen: - focus: "ui" (or "text" or "full") - Returns text description of UI elements, buttons, text content

Ask Specific Questions

You: "Is there a login button visible?" Claude uses describe_screen: - question: "Is there a login button visible?" - Returns: "Yes, there is a blue 'Sign In' button in the top right corner..."

Self-Hosting

Prerequisites

  • Vercel account with Pro plan (for 800s function timeout)

  • Vercel Blob storage

  • Anthropic API key

Deploy Your Own Instance

# Clone the repository git clone https://github.com/anthropics/cua-mcp-server.git cd cua-mcp-server # Install dependencies npm install # Deploy to Vercel vercel --prod

Environment Variables

Variable

Description

Required

CUA_API_KEY

Your CUA Cloud API key

Yes

ANTHROPIC_API_KEY

Anthropic API key for vision processing

Yes

BLOB_READ_WRITE_TOKEN

Vercel Blob token (auto-added)

Yes

CUA_API_BASE

Custom API base URL (default: https://api.cua.ai)

No

CUA_MODEL

Model to use: claude-opus-4-5 (default) or claude-sonnet-4-5

No

Setting Up Vercel Blob

  1. Go to your Vercel project dashboard

  2. Navigate to Storage → Create → Blob

  3. The BLOB_READ_WRITE_TOKEN will be automatically added

Pass API Key Per-Request

If you don't want to store the CUA API key on the server:

{ "mcpServers": { "cua": { "command": "npx", "args": [ "-y", "mcp-remote", "https://your-deployment.vercel.app/mcp", "--header", "X-CUA-API-Key: sk_cua-api01_your-key-here" ] } } }

API Reference

MCP Endpoint

URL: POST /mcp

Content-Type: application/json

Example: Run Task

{ "jsonrpc": "2.0", "method": "tools/call", "id": 1, "params": { "name": "run_task", "arguments": { "sandbox_name": "s-linux-abc123", "task": "Open Firefox and navigate to google.com", "max_steps": 30, "timeout_seconds": 120 } } }

Response:

{ "jsonrpc": "2.0", "id": 1, "result": { "content": [{ "type": "text", "text": "{\"task_id\":\"task_123...\",\"success\":true,\"summary\":\"Opened Firefox, navigated to google.com\",\"steps_taken\":4,\"duration_ms\":8500}" }] } }

Example: Describe Screen

{ "jsonrpc": "2.0", "method": "tools/call", "id": 2, "params": { "name": "describe_screen", "arguments": { "sandbox_name": "s-linux-abc123", "focus": "ui", "question": "Is there a search box visible?" } } }

Model Support

Model

Env Variable

Tool Version

Features

Claude Opus 4.5 (default)

CUA_MODEL=claude-opus-4-5

computer_20251124

Zoom support, higher accuracy

Claude Sonnet 4.5

CUA_MODEL=claude-sonnet-4-5

computer_20250124

Faster, lower cost

Supported Computer Actions

The agent can perform the following actions autonomously:

UI Actions:

  • screenshot - Capture current screen

  • left_click, right_click, double_click, triple_click, middle_click - Mouse clicks at coordinates

  • mouse_move - Move cursor to coordinates

  • left_click_drag - Click and drag from start to end coordinates

  • left_mouse_down, left_mouse_up - Press/release mouse button

  • scroll - Scroll up/down/left/right

  • wait - Pause execution

  • zoom - View specific screen region at full resolution (Opus 4.5 only, defaults to center if no coordinate)

Keyboard:

  • type - Type text

  • key - Press key or key combination (e.g., "ctrl+c")

  • hold_key - Hold a modifier key down (auto-releases after next action)

Constraints

Constraint

Value

Function timeout

800 seconds (Vercel Pro)

Max steps per task

100

Default steps

100

Default timeout

750 seconds

Task history TTL

24 hours

Display resolution

Dynamic (default 1024x768)

Sandbox Types

OS

Size

CPU

RAM

Use Case

Linux

small

2

4GB

Development, testing

Linux

medium

4

8GB

Build tasks, CI/CD

Linux

large

8

16GB

Heavy workloads

Windows

small

2

4GB

Basic Windows apps

Windows

medium

4

8GB

Office, development

Windows

large

8

16GB

Enterprise apps

macOS

small

2

4GB

iOS development

macOS

medium

4

8GB

Xcode builds

macOS

large

8

16GB

Heavy compilation

Regions

  • north-america - US East (lowest latency for US users)

  • europe - EU West

  • asia - Asia Pacific

Troubleshooting

"CUA API key required"

Set CUA_API_KEY environment variable in Vercel or pass via X-CUA-API-Key header.

"ANTHROPIC_API_KEY not configured"

The server needs an Anthropic API key for vision processing. Add it to your Vercel environment variables.

Task times out

  • Default timeout is 750 seconds

  • Reduce task complexity or break into smaller steps

  • Check if sandbox is responsive with describe_screen

Task exceeds max steps

  • Default is 100 steps (max 100)

  • Break complex tasks into smaller subtasks

  • Use more specific task descriptions

Resources

License

MIT

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