[LEGACY — prefer unity_component_set_reference] Set an object reference property on a component via the prefab system. Use unity_component_set_reference instead for richer resolution options.
AI agents use unity_set_object_reference to create or update resources in Unity MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Unity MCP Server environment.
This tool modifies component properties within the Unity prefab system, which creates reversible changes to project assets. It does not execute code, delete data, or move money. While the modification is persistent and affects project state, it remains reversible through undo/version control, placing it in the Write category rather than Execute or Destructive.
From the tool's definition Tool name 'unity_set_object_reference' and description 'Set an object reference property on a component' indicates modification of component properties. The phrase 'via the prefab system' shows it operates on persistent project assets.
Documented attack patterns abuse exactly the kind of access unity_set_object_reference gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Unity MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for unity_set_object_reference:
{
"version": "1",
"default": "deny",
"tools": {
"unity_set_object_reference": {
"limits": [
{
"counter": "unity_set_object_reference_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}unity_set_object_reference 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.
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[LEGACY — prefer unity_component_set_reference] Set an object reference property on a component via the prefab system. Use unity_component_set_reference instead for richer resolution options. It is categorised as a Write tool in the Unity MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Unity MCP Server MCP server in PolicyLayer and add a rule for unity_set_object_reference: 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 Unity MCP Server. Nothing to install.
unity_set_object_reference is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the unity_set_object_reference 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.
Set action: deny in the PolicyLayer policy for unity_set_object_reference. 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.
unity_set_object_reference is provided by the Unity MCP Server MCP server (anklebreaker-studio/unity-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Unity MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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324 Unity MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.