browser_resize · Playwright MCP: Risk & Policy

WHAT IT DOES

What browser_resize does on Playwright MCP

AI agents invoke browser_resize to trigger actions in Playwright MCP. 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_resize needs a policy

Resizing a browser window is an action that modifies the browser's state/environment. It's not a pure read, nor does it write/delete data. It falls under Execute as it triggers an external operation (browser window manipulation). The blast radius is low since it only affects the visual/layout state of the browser session and is easily reversible.

From the tool's definition 'Resize the browser window' — triggers an external browser operation that changes the state of the browser environment

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser_resize Rate-limited

browser_resize 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_resize": {
      "limits": [
        {
          "counter": "browser_resize_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 Playwright MCP, so you can run agents against it safely.

FAQ

Questions about browser_resize

What does the browser_resize tool do? +

Resize the browser window. It is categorised as a Execute tool in the Playwright MCP 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_resize? +

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

What risk level is browser_resize? +

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

Can I rate-limit browser_resize? +

Yes. Add a rate_limit block to the browser_resize 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_resize completely? +

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

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