trace_function · JS Reverse MCP: Risk & Policy

WHAT IT DOES

What trace_function does on JS Reverse MCP

AI agents invoke trace_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 trace_function needs a policy

This tool injects hooks into a running browser process to intercept and trace function calls at runtime. It is part of a server described as enabling 'automated hook injection' and 'browser debugging', meaning it actively instruments executing code. This constitutes execution of debugging/tracing operations within a live browser environment, not merely reading static source.

From the tool's definition Traces calls to a function by its name in the source code... Uses [browser integration implied by server description: 'direct browser integration', 'automated hook injection']

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

trace_function Rate-limited

trace_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": {
    "trace_function": {
      "limits": [
        {
          "counter": "trace_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 trace_function

What does the trace_function tool do? +

Traces calls to a function by its name in the source code. Works for ANY function including module-internal functions (webpack/rollup bundled). Uses. 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 trace_function? +

Register the JS Reverse MCP server in PolicyLayer and add a rule for trace_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 trace_function? +

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

Can I rate-limit trace_function? +

Yes. Add a rate_limit block to the trace_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 trace_function completely? +

Set action: deny in the PolicyLayer policy for trace_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 trace_function? +

trace_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.