set_window_size · Selenium MCP: Risk & Policy

WHAT IT DOES

What set_window_size does on SeleniumMCP

AI agents invoke set_window_size to trigger actions in SeleniumMCP. 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 set_window_size needs a policy

Setting the browser window size is a browser action that affects the state of an active browser session. It fits the Execute category as it triggers an external operation (resizing the browser window). The blast radius is low since it only affects display/layout and has no data or financial implications.

From the tool's definition 'Set the browser window size' — modifies the state of a running browser session, triggering an external browser operation

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_window_size Rate-limited

set_window_size 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": {
    "set_window_size": {
      "limits": [
        {
          "counter": "set_window_size_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 SeleniumMCP, so you can run agents against it safely.

FAQ

Questions about set_window_size

What does the set_window_size tool do? +

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

How do I enforce a policy on set_window_size? +

Register the Selenium MCP server in PolicyLayer and add a rule for set_window_size: 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 SeleniumMCP. Nothing to install.

What risk level is set_window_size? +

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

Can I rate-limit set_window_size? +

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

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

set_window_size is provided by the Selenium MCP server (lokii0911/seleniummcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.