create_material_instance
AI agents use create_material_instance to create or update resources in Uefn — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Uefn environment.
Creating a material instance is a reversible write operation that modifies editor assets. It does not execute arbitrary code, delete data irreversibly, or move money. The blast radius is medium because incorrect material instance creation could affect visual presentation of many actors, but changes can be undone in the editor.
From the tool's definition Tool name 'create_material_instance' indicates creation of a new material instance in UEFN editor. Sibling tools like 'actor_move_to_folder', 'actor_set_label', and 'audio_place' confirm this server performs reversible modifications to editor state.
Documented attack patterns abuse exactly the kind of access create_material_instance gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Uefn, and nothing reaches the server without passing your rules. This is the rule we recommend for create_material_instance:
{
"version": "1",
"default": "deny",
"tools": {
"create_material_instance": {
"limits": [
{
"counter": "create_material_instance_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}create_material_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.
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create_material_instance. It is categorised as a Write tool in the Uefn MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Uefn MCP server in PolicyLayer and add a rule for create_material_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 Uefn. Nothing to install.
create_material_instance 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 create_material_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.
Set action: deny in the PolicyLayer policy for create_material_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.
create_material_instance is provided by the Uefn MCP server (quangdang46/uefn-verse-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Uefn, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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143 Uefn tools catalogued and risk-classified — across an index of 43,000+ MCP servers.