playwright_custom_user_agent · Playwright MCP Server MCP

WHAT IT DOES

What playwright_custom_user_agent does on Playwright MCP Server

AI agents use playwright_custom_user_agent to create or update resources in Playwright MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Playwright MCP Server environment.

WHY IT NEEDS A POLICY

Why playwright_custom_user_agent needs a policy

This tool modifies the browser's User Agent string, which is a configuration change that can be reversed. It doesn't read data, execute code, or destroy anything, but it does alter browser state/settings. The severity is medium because changing the User Agent can be used to spoof identity or bypass user-agent-based restrictions, potentially enabling misuse in web scraping or evading detection.

From the tool's definition 'Set a custom User Agent for the browser' — modifies browser configuration reversibly

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

playwright_custom_user_agent Rate-limited

playwright_custom_user_agent stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "playwright_custom_user_agent": {
      "limits": [
        {
          "counter": "playwright_custom_user_agent_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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 Server, so you can run agents against it safely.

FAQ

Questions about playwright_custom_user_agent

What does the playwright_custom_user_agent tool do? +

Set a custom User Agent for the browser. It is categorised as a Write tool in the Playwright MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on playwright_custom_user_agent? +

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

What risk level is playwright_custom_user_agent? +

playwright_custom_user_agent is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit playwright_custom_user_agent? +

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

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

playwright_custom_user_agent is provided by the Playwright MCP Server MCP server (vinothbhc1986/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.