cmux_browser_snapshot

THE RISK

Low Risk

Why cmux_browser_snapshot needs a policy

This tool retrieves information about the current state of a browser page's DOM and accessibility tree. It performs a read-only query with no side effects, no code execution, and no data modification. The DOM snapshot is informational data used for analysis or monitoring. While the broader CMUX system enables Execute and Write operations, this specific tool is limited to passive inspection.

From the tool's definition Tool name contains 'get' semantic (snapshot retrieval) and description states 'Get a DOM accessibility snapshot' — retrieves page structure/accessibility data without modification or execution.

Documented attack patterns abuse exactly the kind of access cmux_browser_snapshot gives an agent:

POLICY

How to control cmux_browser_snapshot

PolicyLayer is an MCP gateway — it sits between your AI agents and Cmux Agent, and nothing reaches the server without passing your rules. This is the rule we recommend for cmux_browser_snapshot:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "cmux_browser_snapshot": {}
  }
}

cmux_browser_snapshot is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Cmux Agent — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Cmux Agent tools

Destructive cmux_clear_notifications Clear all notifications. Destructive cmux_close_all Close ALL workspaces (or all except specific ones). Use Destructive cmux_close_surface Close a surface (tab). Destructive cmux_close_window Close a window. Destructive cmux_close_workspace Close one or more workspaces and all their panes. Pass a single ref or an array of refs. Execute cmux_browser_console Get or clear browser console logs/errors. Execute cmux_batch Execute multiple CMUX operations in a single MCP call. Each step references an existing cm Execute cmux_browser_eval Execute JavaScript in the browser page.

All 63 Cmux Agent tools →

Read tools on other servers

M-Team MCP Server get_torrent_detail YouTube MCP Server search_channel Android Forensics ADB MCP Server parse_browser_history 0xarchive web3_challenge

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about cmux_browser_snapshot

What does the cmux_browser_snapshot tool do? +

Get a DOM accessibility snapshot of the browser page. It is categorised as a Read tool in the Cmux Agent MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on cmux_browser_snapshot? +

Register the Cmux Agent MCP server in PolicyLayer and add a rule for cmux_browser_snapshot: 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 Cmux Agent. Nothing to install.

What risk level is cmux_browser_snapshot? +

cmux_browser_snapshot is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit cmux_browser_snapshot? +

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

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

cmux_browser_snapshot is provided by the Cmux Agent MCP server (multiagentcognition/cmux-agent-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Cmux Agent tool call.

Start from Cmux Agent, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →