Set the editor selection to specific GameObjects.
AI agents use unity_selection_set 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 the Unity Editor's current selection state by setting it to specific GameObjects. It changes editor state (what is selected) but does not delete, execute code, or move money. The effect is reversible (selection can be changed again), making it a Write operation.
From the tool's definition Set the editor selection to specific GameObjects
Documented attack patterns abuse exactly the kind of access unity_selection_set 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_selection_set:
{
"version": "1",
"default": "deny",
"tools": {
"unity_selection_set": {
"limits": [
{
"counter": "unity_selection_set_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
} unity_selection_set 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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Set the editor selection to specific GameObjects. 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_selection_set: 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_selection_set 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_selection_set 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_selection_set. 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_selection_set 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.