hook_function · JS Reverse MCP: Risk & Policy

WHAT IT DOES

What hook_function does on JS Reverse MCP

AI agents invoke hook_function 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 hook_function needs a policy

This tool injects hooks into running browser/JavaScript functions to intercept calls, arguments, and return values. This is an active code injection operation that modifies the runtime behavior of a target script/application — fitting the Execute category.

From the tool's definition hook a function and log calls/args/results without pausing execution

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

hook_function Rate-limited

hook_function 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": {
    "hook_function": {
      "limits": [
        {
          "counter": "hook_function_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 hook_function

What does the hook_function tool do? +

Recommended default for reverse engineering: hook a function and log calls/args/results without pausing execution. 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 hook_function? +

Register the JS Reverse MCP server in PolicyLayer and add a rule for hook_function: 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 hook_function? +

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

Can I rate-limit hook_function? +

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

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

hook_function 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.