create_session · Selenium MCP: Risk & Policy

WHAT IT DOES

What create_session does on Selenium

AI agents invoke create_session to trigger actions in Selenium. 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 create_session needs a policy

This tool launches a browser process (Chrome headless by default), which is an external operation with side effects — consuming system resources, enabling subsequent browser automation actions, and potentially making network requests. It triggers external operations whose effects depend on arguments (e.g., browser type, options), placing it in the Execute category.

From the tool's definition Create a new browser session. Defaults to Chrome headless.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_session Rate-limited

create_session 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": {
    "create_session": {
      "limits": [
        {
          "counter": "create_session_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 Selenium, so you can run agents against it safely.

FAQ

Questions about create_session

What does the create_session tool do? +

Create a new browser session. Defaults to Chrome headless. It is categorised as a Execute tool in the Selenium MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on create_session? +

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

What risk level is create_session? +

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

Can I rate-limit create_session? +

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

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

create_session is provided by the Selenium MCP server (scv-consultants/selenium-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.