browser_pdf · Wmux MCP: Risk & Policy

WHAT IT DOES

What browser_pdf does on Wmux

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

WHY IT NEEDS A POLICY

Why browser_pdf needs a policy

This tool creates a new PDF file from the current page state. While it produces an output file, it does not modify or delete existing data, nor does it execute arbitrary code or move money. The operation is reversible (the PDF can be deleted), and the blast radius is low since a PDF export has no side effects on the underlying system or data being viewed.

From the tool's definition Tool description states it 'Export[s] the current page as a PDF file', which creates a new file artifact. The verb 'export' combined with file creation indicates data is being written to disk.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser_pdf Rate-limited

browser_pdf 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": {
    "browser_pdf": {
      "limits": [
        {
          "counter": "browser_pdf_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 Wmux, so you can run agents against it safely.

FAQ

Questions about browser_pdf

What does the browser_pdf tool do? +

Export the current page as a PDF file. Falls back to CDP Page.printToPDF when Playwright pdf() is unavailable (e.g. CDP-connected browsers). It is categorised as a Write tool in the Wmux MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on browser_pdf? +

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

What risk level is browser_pdf? +

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

Can I rate-limit browser_pdf? +

Yes. Add a rate_limit block to the browser_pdf 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_pdf completely? +

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

browser_pdf is provided by the Wmux MCP server (openwong2kim/wmux). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.