Claude Code¶

Wire justpen-browser-mcp into Claude Code.

Prerequisites¶

Claude Code installed and authenticated
justpen-browser-mcp installed and on PATH (see Install)

Registration¶

Add to your Claude Code MCP config:

{
  "mcpServers": {
    "justpen-browser": {
      "command": "justpen-browser-mcp"
    }
  }
}

Running outside the install venv¶

If Claude Code runs outside the venv where justpen-browser-mcp is installed, use an explicit interpreter path:

{
  "mcpServers": {
    "justpen-browser": {
      "command": "/absolute/path/to/.venv/bin/python",
      "args": ["-m", "justpen_browser_mcp"]
    }
  }
}

Telemetry¶

For stdio, add an env object inside the mcpServers.justpen-browser entry:

{
  "env": {
    "JUSTPEN_BROWSER_OTEL_ENABLED": "true",
    "JUSTPEN_BROWSER_OTEL_ENDPOINT": "http://127.0.0.1:4318",
    "JUSTPEN_SESSION_ID": "pentest-example",
    "JUSTPEN_BROWSER_OTEL_RESOURCE_ATTRIBUTES": "justpen.run.id=run-example"
  }
}

For HTTP, set these variables on the separately started server process. See Telemetry for session ownership, collector settings and the measured native tracing limits.

Sanity check¶

After registering, ask Claude Code to list available MCP servers / tools. The justpen-browser server should appear with its lifecycle, navigation, and interaction tools.

Common pitfalls¶

command not found — the justpen-browser-mcp script is not on the PATH Claude Code sees. Use the absolute-path form above.
Headless mode — browser_create_instance defaults to headless=true. Pass headless=false to the tool call when you want to watch the browser for debugging.
Transport selection — these examples use stdio. The server also supports HTTP when started with --transport http; configure your client for Streamable HTTP at http://127.0.0.1:8931/mcp to use it. See Run the server, including its warning about the lack of built-in authentication.

Reference¶

Canonical Claude Code MCP config docs: see the Claude Code documentation site for the up-to-date config schema.