stop_trace · Unreal MCP: Risk & Policy

WHAT IT DOES

What stop_trace does on Unreal

AI agents invoke stop_trace to trigger actions in Unreal. 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 stop_trace needs a policy

This tool triggers an operation that stops a live trace session in Unreal Engine's profiling infrastructure. While not permanently destructive (the trace data already collected typically persists), it executes a command that halts an ongoing external process. This is an Execute action rather than Read (it modifies system state) or Destructive (the action is reversible—a new trace can be started).

From the tool's definition 'Stop the active Unreal Insights trace session' - this terminates an active tracing operation, which is an externally-observable action that affects the state of a running profiling/debugging system.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

stop_trace Rate-limited

stop_trace 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": {
    "stop_trace": {
      "limits": [
        {
          "counter": "stop_trace_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 Unreal, so you can run agents against it safely.

FAQ

Questions about stop_trace

What does the stop_trace tool do? +

Stop the active Unreal Insights trace session. It is categorised as a Execute tool in the Unreal MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on stop_trace? +

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

What risk level is stop_trace? +

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

Can I rate-limit stop_trace? +

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

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

stop_trace is provided by the Unreal MCP server (sam-david/unreal-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.