nullprint-mcp

nullprint-mcp (Node build)

An MCP server for Nullprint, the multi-profile browser. It lets any MCP-capable AI agent (Claude Code, Claude Desktop, Cursor, Windsurf, Cline, OpenAI Codex, Kimi, …) create browser profiles, launch them, run consistency check-ups and drive the pages inside a running profile.

This is the Node.js build: a single bundled file with no runtime dependencies, so npx nullprint-mcp works wherever Node 18+ is present, with no Python or uv on the machine. The Python build on PyPI (uvx nullprint-mcp) exposes the same 18 tools with the same names, arguments and behaviour; pick whichever runtime your client already has.

The server is a thin layer over the local Nullprint daemon's HTTP API: every tool maps to one daemon endpoint. The daemon, the browser kernels and the fingerprint engine ship with the Nullprint desktop app and are not part of this package.

Requirements

• Nullprint desktop app installed and running (Windows or macOS), signed in. Download: https://nullprint.ai
• Node.js 18 or newer on the same machine.

Install

# Claude Code
claude mcp add nullprint -- npx -y nullprint-mcp

# OpenAI Codex
codex mcp add nullprint -- npx -y nullprint-mcp

Claude Desktop, Cursor, Windsurf, Cline, Kimi and other clients that use an mcpServers config file:

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

No port or key to configure: the server reads the running daemon's port and API key from ~/.nullprint/daemon.json, which the desktop app writes on start-up. To point at a daemon elsewhere, pass --daemon-url http://host:port (or --port 7801 for localhost) and set NULLPRINT_API_KEY. Resolution order, most explicit first:

• --daemon-url / --port
• NULLPRINT_DAEMON_URL
• NULLPRINT_PORT
• ~/.nullprint/daemon.json (NULLPRINT_HOME changes the directory)

If the daemon is not running the tools say so plainly instead of throwing a connection trace.

Tools

Tool	What it does
profiles_list	List every profile with status (running / idle), exit and ledger metadata
profile_start	Open a browser session for a profile; returns the driving endpoints
profile_stop	Stop that profile's browser (session or app-launched window)
profile_create	Create a profile (fingerprint generated and frozen), optionally with proxy, ledger and start pages
profile_settings	Change a display setting of an existing profile — today force_dark (force dark web pages, off by default; merged into its launch settings)
profile_checkup	Consistency check-up, returns {summary, checks}
proxy_check	Stateless proxy test: exit IP, country, latency
profile_delete	Soft delete to the recycle bin (recoverable); refused while running
trash_list	Read-only list of recoverable profiles in the recycle bin
profile_restore	Restore from the recycle bin with fingerprint, proxy and logins intact
session_goto	Navigate the session's current page
session_snapshot	Accessibility tree of the current page (find selectors, read state)
session_click_selector	Click an element by CSS selector
session_fill_selector	Fill an input by CSS selector
session_press	Send a key (e.g. Enter)
session_eval	Run JavaScript on the page, returns {ok, result}
session_tabs	List the session's tabs and the active one
session_switch_tab	Bring a tab to the front
session_dialog	Answer the JavaScript dialog (alert / confirm / prompt / beforeunload) open on the page: accept or dismiss

session_* tools drive the warm session opened by profile_start; on a profile without one they return 409 and tell the agent to start it first. Permanent deletion is deliberately not exposed: emptying the recycle bin is a human action in the desktop app.

Development

npm install
npm run typecheck
npm test          # builds dist/index.js, then runs the stdio contract tests against a fake daemon
node dist/index.js --help

Nothing may be printed to stdout: stdout is the MCP channel. Diagnostics go to stderr.

License

MIT. Copyright (c) 2026 HENGCHENG LLC.

中文说明

这是 Nullprint（多身份指纹浏览器）MCP 服务的 Node 版：单文件、零运行时依赖，只要机器上有 Node 18+，npx nullprint-mcp 就能跑，不需要 Python 或 uv。PyPI 上的 Python 版（uvx nullprint-mcp）提供同样的 17 个工具，名字、参数、行为完全一致，按你的客户端自带哪个运行时选。

接入：

claude mcp add nullprint -- npx -y nullprint-mcp      # Claude Code
codex mcp add nullprint -- npx -y nullprint-mcp       # OpenAI Codex

Claude Desktop、Cursor、Windsurf、Cline、Kimi 等走配置文件的客户端，在 mcpServers 里加 {"command": "npx", "args": ["-y", "nullprint-mcp"]}。

不用配端口和密钥：服务自动读桌面应用写在 ~/.nullprint/daemon.json 里的端口和 API Key。要连别的机器上的 daemon，传 --daemon-url 并设 NULLPRINT_API_KEY。