set_niagara_bool · Unreal MCP: Risk & Policy

WHAT IT DOES

What set_niagara_bool does on Unreal

AI agents use set_niagara_bool to create or update resources in Unreal — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Unreal environment.

WHY IT NEEDS A POLICY

Why set_niagara_bool needs a policy

This tool creates or modifies data (a boolean parameter) within a Niagara visual effects component. Changes to Niagara parameters are reversible by setting them back to previous values, making this a Write operation rather than Destructive or Execute.

From the tool's definition The tool name 'set_niagara_bool' and description 'Set a bool parameter on a Niagara component' indicate it modifies a parameter on a Niagara particle system component, which is a reversible state change within Unreal Engine.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_niagara_bool Rate-limited

set_niagara_bool stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "set_niagara_bool": {
      "limits": [
        {
          "counter": "set_niagara_bool_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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 set_niagara_bool

What does the set_niagara_bool tool do? +

Set a bool parameter on a Niagara component. It is categorised as a Write tool in the Unreal MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_niagara_bool? +

Register the Unreal MCP server in PolicyLayer and add a rule for set_niagara_bool: 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 set_niagara_bool? +

set_niagara_bool is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit set_niagara_bool? +

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

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

set_niagara_bool 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.