box by Simular

box is a cloud Linux desktop for your coding agent. Add it to Claude Code, Codex or Cursor as a remote MCP server and the agent can use a real computer: open a browser, click, type, read the screen and run commands.

Key facts

• Product: box, from Simular. Portal: https://box.simular.ai.
• Interface: one hosted MCP server, box (https://relay.simular.cloud/mcp), authenticated with your API key (Authorization: Bearer sapi_...). Its tools work on your box (shell, browser, screenshot, desktop tools), waking it when it sleeps, and manage it (list, wake, save, restore). No local package to install.
• The computer: one cloud Linux desktop per account. It sleeps when no one uses it and wakes when your agent connects.
• Cost: the box itself is free. Its model calls use your account's daily credits.

Getting started

1. Sign in with Google at https://box.simular.ai/sign-in. Your first API key is created for you; keys start with sapi_.
2. Easiest: tell your coding agent Set up box from https://box.simular.ai/install and it does the rest. To do it yourself, add the server below, replacing sapi_YOUR_KEY with your key.
3. Ask the agent for a task, for example: Use box to open Chrome, search Google for "Simular", and summarize the top 3 results.

Claude Code

claude mcp add --transport http box https://relay.simular.cloud/mcp --header "Authorization: Bearer sapi_YOUR_KEY"

Codex

# ~/.codex/config.toml
[mcp_servers.box]
url = "https://relay.simular.cloud/mcp"
http_headers = { "Authorization" = "Bearer sapi_YOUR_KEY" }

Cursor

{
  "mcpServers": {
    "box": {
      "url": "https://relay.simular.cloud/mcp",
      "headers": {
        "Authorization": "Bearer sapi_YOUR_KEY"
      }
    }
  }
}