arc-browser-mcp

MCP server that controls Arc via AppleScript, with optional CDP (remote-debugging-port) support for reading console/network events.

Requirements

• macOS (Arc AppleScript)
• Arc
• Bun

Install

bun install

Run

bun run dev

bunx

After publishing to npm, you can run it without cloning:

bunx --package @alango/arc-devtools-mcp arc-devtools-mcp

Tools

AppleScript:

• arc_list_spaces
• arc_focus_space
• arc_list_tabs
• arc_get_active_tab
• arc_open_url
• arc_focus_tab
• arc_close_tab
• arc_reload_tab
• arc_execute_js

CDP (remote debugging):

• arc_cdp_status
• arc_cdp_connect
• arc_cdp_disconnect
• arc_cdp_get_console
• arc_cdp_get_network

OpenCode configuration

Add an MCP entry pointing at this repo:

{
  "mcp": {
    "arc": {
      "command": "bash",
      "args": [
        "-lc",
        "cd /Users/alan/Developments/arc-browser-mcp && bun run dev"
      ]
    }
  }
}

Examples

List tabs:

{"tool":"arc_list_tabs","input":{}}

Open a URL:

{"tool":"arc_open_url","input":{"url":"https://example.com"}}

Execute JS in active tab:

{"tool":"arc_execute_js","input":{"javascript":"console.log('hello from mcp')"}}

Connect to CDP and read console/network:

{"tool":"arc_cdp_connect","input":{"port":9222}}

{"tool":"arc_cdp_get_console","input":{"limit":50}}

{"tool":"arc_cdp_get_network","input":{"limit":200}}

CDP (Console / Network)

Arc's remote debugging WebSocket can reject non-DevTools clients unless you allow the Origin.

To enable CDP for this server:

1. Quit Arc

osascript -e 'tell application "Arc" to quit'

2. Relaunch Arc with flags

open -na "Arc" --args \
  --remote-debugging-port=9222 \
  --remote-allow-origins=http://127.0.0.1

If you want to allow any Origin (less strict):

open -na "Arc" --args \
  --remote-debugging-port=9222 \
  --remote-allow-origins=*

Environment variables

• ARC_MCP_CDP_ORIGIN (default: http://127.0.0.1)
  • Must match what you pass to --remote-allow-origins=... (unless you use *).
• ARC_MCP_ARC_USER_DATA_DIR
  • Overrides the Arc user data dir used to read DevToolsActivePort.

Troubleshooting

• 403 Forbidden / "Rejected an incoming WebSocket connection"
  • Arc was launched without the matching --remote-allow-origins=....
  • Fix: restart Arc with --remote-allow-origins=http://127.0.0.1 (or *).
• http://127.0.0.1:9222/json/version returns 404
  • This can happen in Arc. This server falls back to DevToolsActivePort for browser WebSocket discovery.
• Port is listening but connect fails intermittently
  • Arc can restart/rotate the DevToolsActivePort UUID. Re-run arc_cdp_connect.