Apply a material preset to selected actors.
AI agents use material_apply_preset 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.
This tool modifies material properties of actors in the UEFN editor, which is a reversible change to object state. It does not delete data (Destructive), execute arbitrary code (Execute), involve financial transactions (Financial), or merely read data (Read). The modification of visual/material properties on game actors qualifies as Write.
From the tool's definition Tool applies a material preset to selected actors. 'Apply' indicates modification of visual properties on existing game objects.
Documented attack patterns abuse exactly the kind of access material_apply_preset 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 material_apply_preset:
{
"version": "1",
"default": "deny",
"tools": {
"material_apply_preset": {
"limits": [
{
"counter": "material_apply_preset_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}material_apply_preset 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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Apply a material preset to selected actors. 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 material_apply_preset: 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.
material_apply_preset 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 material_apply_preset 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 material_apply_preset. 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.
material_apply_preset 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.
Free to start. No card required.
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