set_prefab_ref

Set a GameObject-typed property on a component to a loaded prefab. Use this when set_property can

SERVERSbox SOURCEsbox-mcp-server

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/sbox/set-prefab-ref.md

WHAT IT DOES

What set_prefab_ref does on Sbox

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

RISK

Why set_prefab_ref is rated Medium

This tool modifies game object properties by assigning prefab references to components. This is a reversible Write operation—the property can be changed or removed. While it affects game state, it does not execute arbitrary code, delete data irreversibly, or move money. The blast radius is medium because incorrect prefab assignments could corrupt game logic or visuals, but changes can be undone.

From the tool's definition Tool name 'set_prefab_ref' and description indicate it 'Set[s] a GameObject-typed property on a component to a loaded prefab', which modifies component properties.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs set_prefab_ref safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Sbox, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For set_prefab_ref, this is the rule to start with:

set_prefab_ref Rate-limited

set_prefab_ref 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_prefab_ref": {
      "limits": [
        {
          "counter": "set_prefab_ref_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Sbox, apply this rule, and every set_prefab_ref call is checked against it from then on.

FAQ

Questions about set_prefab_ref

What does the set_prefab_ref tool do? +

Set a GameObject-typed property on a component to a loaded prefab. Use this when set_property can. It is categorised as a Write tool in the Sbox 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_prefab_ref? +

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

What risk level is set_prefab_ref? +

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

Can I rate-limit set_prefab_ref? +

Yes. Add a rate_limit block to the set_prefab_ref 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_prefab_ref completely? +

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

set_prefab_ref is provided by the Sbox MCP server (sbox-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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