start_browser · MCP Selenium WebDriver MCP: Risk & Policy

WHAT IT DOES

What start_browser does on MCP Selenium WebDriver

AI agents invoke start_browser to trigger actions in MCP Selenium WebDriver. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why start_browser needs a policy

start_browser initiates browser processes and establishes automation sessions, enabling Execute-category actions (arbitrary code execution via execute_script, navigation, form submission, etc.). While starting a browser alone is not destructive or financial, it is a prerequisite for potentially harmful actions and represents code/process execution.

From the tool's definition Tool is part of a Selenium WebDriver MCP server explicitly described as enabling 'browser automation.' Starting a browser is a foundational action that initiates external browser processes whose subsequent behavior depends on caller intent.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

start_browser Rate-limited

start_browser stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "start_browser": {
      "limits": [
        {
          "counter": "start_browser_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches MCP Selenium WebDriver, so you can run agents against it safely.

FAQ

Questions about start_browser

What does the start_browser tool do? +

start_browser. It is categorised as a Execute tool in the MCP Selenium WebDriver MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on start_browser? +

Register the MCP Selenium WebDriver MCP server in PolicyLayer and add a rule for start_browser: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches MCP Selenium WebDriver. Nothing to install.

What risk level is start_browser? +

start_browser is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit start_browser? +

Yes. Add a rate_limit block to the start_browser rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block start_browser completely? +

Set action: deny in the PolicyLayer policy for start_browser. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides start_browser? +

start_browser is provided by the MCP Selenium WebDriver MCP server (nixon-suarez/mcp-selenium-webdriver). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.