spawn_blueprint_actor · Unreal MCP: Risk & Policy

WHAT IT DOES

What spawn_blueprint_actor does on Unreal

AI agents use spawn_blueprint_actor 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 spawn_blueprint_actor needs a policy

Spawning an actor creates a new object in the level, which is a reversible write operation (the actor can be deleted). It does not execute code, delete data, or involve financial transactions.

From the tool's definition Spawn an instance of a Blueprint class in the level

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

spawn_blueprint_actor Rate-limited

spawn_blueprint_actor 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": {
    "spawn_blueprint_actor": {
      "limits": [
        {
          "counter": "spawn_blueprint_actor_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 spawn_blueprint_actor

What does the spawn_blueprint_actor tool do? +

Spawn an instance of a Blueprint class in the level. 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 spawn_blueprint_actor? +

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

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

Can I rate-limit spawn_blueprint_actor? +

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

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

spawn_blueprint_actor 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.