Clone an object with optional position offset
AI agents use duplicate_entity to create or update resources in Threlte — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Threlte environment.
The tool creates a duplicate/clone of an existing object in a Three.js/Threlte scene. This is a Write operation because it adds new data to the scene state in a reversible manner (the cloned object can be deleted). The severity is medium because uncontrolled duplication could degrade scene performance or create unwanted visual artifacts, but these effects are reversible via deletion.
From the tool's definition Tool description states 'Clone an object with optional position offset' - this creates a new entity in the scene, which is a reversible write operation.
Documented attack patterns abuse exactly the kind of access duplicate_entity gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Threlte, and nothing reaches the server without passing your rules. This is the rule we recommend for duplicate_entity:
{
"version": "1",
"default": "deny",
"tools": {
"duplicate_entity": {
"limits": [
{
"counter": "duplicate_entity_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}duplicate_entity 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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Clone an object with optional position offset. It is categorised as a Write tool in the Threlte MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Threlte MCP server in PolicyLayer and add a rule for duplicate_entity: 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 Threlte. Nothing to install.
duplicate_entity 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 duplicate_entity 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 duplicate_entity. 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.
duplicate_entity is provided by the Threlte MCP server (serifeusstudio/threlte-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Threlte, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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