Stop the running scenario. By default also exits Play mode on the main editor so
AI agents invoke unity_mppm_stop to trigger actions in Unity MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
This tool executes an action that triggers external operations (stopping a scenario and exiting Play mode in Unity Editor) whose effects depend on the current state of the editor. While the action is reversible (Play mode can be restarted), it actively manipulates running processes and editor state, placing it in the Execute category rather than Write.
From the tool's definition Tool name 'unity_mppm_stop' and description 'Stop the running scenario. By default also exits Play mode on the main editor' indicates it stops/terminates active processes and changes editor state.
Documented attack patterns abuse exactly the kind of access unity_mppm_stop 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_mppm_stop:
{
"version": "1",
"default": "deny",
"tools": {
"unity_mppm_stop": {
"limits": [
{
"counter": "unity_mppm_stop_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
} unity_mppm_stop stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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Stop the running scenario. By default also exits Play mode on the main editor so. It is categorised as a Execute tool in the Unity MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Unity MCP Server MCP server in PolicyLayer and add a rule for unity_mppm_stop: 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_mppm_stop is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the unity_mppm_stop 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_mppm_stop. 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_mppm_stop 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.
Deterministic rules across all 324 Unity MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
324 Unity MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.