hover_element · JS Reverse MCP: Risk & Policy

WHAT IT DOES

What hover_element does on JS Reverse MCP

AI agents invoke hover_element to trigger actions in JS Reverse MCP. 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 hover_element needs a policy

This tool triggers a browser action (hovering over a DOM element), which can cause side effects such as triggering JavaScript event handlers (mouseover, mouseenter), revealing hidden menus, or initiating network requests. It is not a pure read operation since it actively interacts with the browser environment and can cause dynamic behavior to execute.

From the tool's definition Hover over an element by selector

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

hover_element Rate-limited

hover_element 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": {
    "hover_element": {
      "limits": [
        {
          "counter": "hover_element_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 JS Reverse MCP, so you can run agents against it safely.

FAQ

Questions about hover_element

What does the hover_element tool do? +

Hover over an element by selector. It is categorised as a Execute tool in the JS Reverse MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on hover_element? +

Register the JS Reverse MCP server in PolicyLayer and add a rule for hover_element: 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 JS Reverse MCP. Nothing to install.

What risk level is hover_element? +

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

Can I rate-limit hover_element? +

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

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

hover_element is provided by the JS Reverse MCP server (noone-hub/jsreverser-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.