unity_select_instance

THE RISK

Medium Risk

Why unity_select_instance needs a policy

This tool modifies session state by setting the active Unity Editor instance for subsequent operations. It doesn't read data passively—it configures which instance all future commands will target, which could have significant downstream effects if the wrong instance is selected.

From the tool's definition Select which Unity Editor instance to work with for this session

Documented attack patterns abuse exactly the kind of access unity_select_instance gives an agent:

POLICY

How to control unity_select_instance

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_select_instance:

policy.json

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

unity_select_instance 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.

Create a free account and register Unity MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Unity MCP Server tools

Destructive unity_amplify_remove_node Remove a node from the currently open Amplify Shader Editor graph by its unique ID. Cannot Destructive unity_animation_remove_curve Remove an entire animation curve binding from a clip. Useful for cleaning up or restructur Destructive unity_animation_remove_event Remove an animation event by its index. Use get_animation_events first to find the index. Destructive unity_animation_remove_keyframe Remove a keyframe from an animation curve by its index. Use get_curve_keyframes first to f Destructive unity_animation_remove_layer Remove a layer from an Animator Controller by index. Cannot remove the base layer (index 0 Destructive unity_animation_remove_parameter Remove a parameter from an Animator Controller by name. Destructive unity_animation_remove_state Remove a state from an Animator Controller layer. Destructive unity_animation_remove_transition Remove a transition from an Animator Controller state. Can target by source/destination na

All 324 Unity MCP Server tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about unity_select_instance

What does the unity_select_instance tool do? +

Select which Unity Editor instance to work with for this session. 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.

How do I enforce a policy on unity_select_instance? +

Register the Unity MCP Server MCP server in PolicyLayer and add a rule for unity_select_instance: 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.

What risk level is unity_select_instance? +

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

Can I rate-limit unity_select_instance? +

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

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

unity_select_instance 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.

Enforce policy on every Unity MCP Server tool call.

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.

CHECK YOUR STACK →