Nullprint MCP Server認証済み注目

What is Nullprint MCP Server?

Nullprint MCP Server is an open-source local server that lets Claude Code, Claude Desktop, OpenAI Codex, Kimi and other MCP agents create, launch, check and drive browser profiles in Nullprint, the AI antidetect browser.

The server (nullprint-mcp, MIT-licensed, by HENGCHENG LLC) is a thin layer over the Local API that the Nullprint desktop app runs on your computer. Every tool maps to one daemon endpoint. The daemon, browser kernels and fingerprint engine ship with the closed desktop app and are not part of the package. The MCP layer talks to the daemon on 127.0.0.1 and sends nothing to Nullprint's servers.

How to use Nullprint MCP Server?

Requirements:

• The Nullprint desktop app installed, signed in and running on the same computer (Windows or macOS). Download it from nullprint.ai.
• Python 3.11+ and uv, which fetches the package on first run. A Node.js 18+ build is also published on npm with the same 17 tools.

There is no port or key to configure: the server reads the running daemon's port and API key from ~/.nullprint/daemon.json, which the app writes on start-up.

Claude Code

claude mcp add nullprint -- uvx nullprint-mcp
# or the Node build
claude mcp add nullprint -- npx -y nullprint-mcp

OpenAI Codex

codex mcp add nullprint -- uvx nullprint-mcp

Claude Desktop

The Nullprint docs offer a .mcpb extension you can double-click to install; Claude Desktop then manages Python and dependencies. Or add this to the config file:

{
  "mcpServers": {
    "nullprint": {
      "command": "uvx",
      "args": ["nullprint-mcp"]
    }
  }
}

Without uv, run pip install nullprint-mcp and use nullprint-mcp as the command with no arguments.

Cursor

Cursor, Windsurf, Cline, Kimi and Qwen use the same mcpServers format. With Node:

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

VS Code

Add a stdio entry with the same command to your VS Code MCP configuration:

{
  "servers": {
    "nullprint": {
      "type": "stdio",
      "command": "uvx",
      "args": ["nullprint-mcp"]
    }
  }
}

Restart the client and try: "List my Nullprint profiles and tell me which ones are running."

Daemon on another machine: pass --daemon-url http://host:port (or --port for localhost) and set NULLPRINT_API_KEY. Resolution order is --daemon-url/--port, then NULLPRINT_DAEMON_URL, then NULLPRINT_PORT, then ~/.nullprint/daemon.json (NULLPRINT_HOME changes the directory). The daemon listens on localhost only; the docs say to reach it over an SSH tunnel or private network, never the public internet.

Key features of Nullprint MCP Server

• Create profiles with a generated and frozen fingerprint, optionally with a proxy, ledger and start pages.
• Run consistency check-ups on profiles and test proxies for exit IP, country and latency.
• Start and stop profile browsers and drive pages inside a running session with CSS selectors.
• Recoverable deletion: profiles go to a recycle bin and can be restored with fingerprint, proxy and logins intact.
• Deliberate safety limits: no permanent-delete tool and no file-writing or screenshot-to-disk tools.
• Python (uvx) and Node (npx) builds with identical tool names and arguments.

Nullprint MCP Server tools

The server exposes 17 tools.

• Profiles: profiles_list, profile_create, profile_checkup, profile_start, profile_stop, profile_delete, trash_list and profile_restore. profile_start returns the driving endpoints, plus a cdp_endpoint DevTools address for Chrome kernels. profile_delete is refused while a profile is running.
• Proxies: proxy_check is a stateless proxy test; an unreachable proxy comes back as data, not an error.
• Sessions: session_goto, session_snapshot (accessibility tree), session_click_selector, session_fill_selector, session_press, session_eval (returns {ok, result}), session_tabs and session_switch_tab. These need a session opened by profile_start, or they return 409.

Use cases of Nullprint MCP Server

• Bulk setup: "Create 20 profiles from this CSV of proxies, run a check-up on each and tell me which ones are not Consistent."
• Reading account pages: "Open profile shop-07, go to the orders page and read me the unfulfilled orders."
• Proxy testing: "Test these 5 proxies and tell me the exit country and latency of each."
• Housekeeping: "Which profiles are running right now? Stop the ones that have been idle for an hour."

Troubleshooting Nullprint MCP Server

• Tools say the daemon is not running: start and sign in to the Nullprint desktop app, which writes ~/.nullprint/daemon.json on start-up.
• session_* tools return 409: the profile has no open session. Call profile_start first.
• A click or fill fails: selectors are CSS, not XPath or role/name. Call session_snapshot to find one.
• profile_create returns 422: an unknown engine value. Leave it empty to use the app's default kernel.
• Profile becomes detectable after attaching Playwright: an outside tool driving the CDP endpoint bypasses Nullprint's consistency guards. Prefer the session_* tools.