apply_material

Apply a material to an actor's mesh component.

SERVERUnreal SOURCE@jjpxdev/unreal-mcp

Medium RISK CLASS

Category Write

Parameters 32 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/jjpxdev-unreal-mcp/apply-material.md

WHAT IT DOES

What apply_material does on Unreal

AI agents use apply_material to create or update resources in Unreal, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Unreal environment.

Parameter	Type	Required	Description
`actor_name`	string	Yes	Actor name or label
`slot_index`	number	—	Material slot index
`material_path`	string	Yes	Material asset path

Parameters from the server's own tool schema.

RISK

Why apply_material is rated Medium

An AI agent can call apply_material faster than any human can review: one bad instruction and it creates or modifies resources in Unreal by the hundred, each call as confident as the last.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs apply_material safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Unreal, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For apply_material, this is the rule to start with:

apply_material Rate-limited

apply_material 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.

View as policy code

policy.json

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

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Unreal, apply this rule, and every apply_material call is checked against it from then on.

FAQ

Questions about apply_material

What does the apply_material tool do? +

Apply a material to an actor's mesh component. It is categorised as a Write tool in the Unreal MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

What parameters does apply_material accept? +

apply_material accepts 3 parameters: actor_name, slot_index, material_path. Required: actor_name, material_path. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on apply_material? +

Register the Unreal MCP server in PolicyLayer and add a rule for apply_material: 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 Unreal. Nothing to install.

What risk level is apply_material? +

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

Can I rate-limit apply_material? +

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

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

apply_material is provided by the Unreal MCP server (@jjpxdev/unreal-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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