browser_new_window · Browser MCP: Risk & Policy

WHAT IT DOES

What browser_new_window does on BrowserMCP

AI agents invoke browser_new_window to trigger actions in BrowserMCP. 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 browser_new_window needs a policy

browser_new_window triggers real processes with real consequences. An agent gone sideways doesn't fire it once — it starts dozens of builds, sends mass notifications, or burns through compute before anyone looks up.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser_new_window Rate-limited

browser_new_window 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": {
    "browser_new_window": {
      "limits": [
        {
          "counter": "browser_new_window_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 BrowserMCP, so you can run agents against it safely.

FAQ

Questions about browser_new_window

What does the browser_new_window tool do? +

Open a new browser window. It is categorised as a Execute tool in the BrowserMCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on browser_new_window? +

Register the Browser MCP server in PolicyLayer and add a rule for browser_new_window: 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 BrowserMCP. Nothing to install.

What risk level is browser_new_window? +

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

Can I rate-limit browser_new_window? +

Yes. Add a rate_limit block to the browser_new_window 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 browser_new_window completely? +

Set action: deny in the PolicyLayer policy for browser_new_window. 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 browser_new_window? +

browser_new_window is provided by the Browser MCP server (smotree/browsermcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.