browser_tab_new · MCP Macaco Playwright MCP: Risk & Policy

WHAT IT DOES

What browser_tab_new does on MCP Macaco Playwright

AI agents invoke browser_tab_new to trigger actions in MCP Macaco Playwright. 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_tab_new needs a policy

This tool performs an action that executes external operations (browser tab creation and navigation) rather than simply reading data. While not destructive or financial, it triggers browser behavior dependent on supplied arguments. The ability to navigate to arbitrary URLs means an agent could be directed to visit malicious sites, perform unwanted web interactions, or initiate workflows with side effects.

From the tool's definition Tool creates a new browser tab and navigates to a URL, triggering external browser operations whose effects depend on the URL argument provided.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser_tab_new Rate-limited

browser_tab_new 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_tab_new": {
      "limits": [
        {
          "counter": "browser_tab_new_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 Macaco Playwright, so you can run agents against it safely.

FAQ

Questions about browser_tab_new

What does the browser_tab_new tool do? +

Create a new browser tab and optionally navigate to a specific URL. If no URL is provided, the new tab will remain blank. After creation, automatically captures a page snapshot of the new tab. It is categorised as a Execute tool in the MCP Macaco Playwright 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_tab_new? +

Register the MCP Macaco Playwright MCP server in PolicyLayer and add a rule for browser_tab_new: 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 Macaco Playwright. Nothing to install.

What risk level is browser_tab_new? +

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

Can I rate-limit browser_tab_new? +

Yes. Add a rate_limit block to the browser_tab_new 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_tab_new completely? +

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

browser_tab_new is provided by the MCP Macaco Playwright MCP server (macacoai/mcp-playwright). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.