connect_material_property
Connect an expression to a material output property (BaseColor, Normal, Metallic, Roughness, etc.).
This record as markdown: /tools/jjpxdev-unreal-mcp/connect-material-property.md
What connect_material_property does on Unreal
AI agents use connect_material_property 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 |
|---|---|---|---|
output_name | string | — | Expression output pin name (empty string for first/default output) |
material_path | string | Yes | Material asset path |
expression_name | string | Yes | Expression name to connect |
material_property | string | Yes | Material property to connect to |
Parameters from the server's own tool schema.
Why connect_material_property is rated Medium
This tool creates or modifies material properties within Unreal Engine, which is a reversible operation (connections can be disconnected or replaced). It does not execute arbitrary code, delete assets, or cause financial transactions. It fits the Write category as it creates/modifies data (material property connections).
From the tool's definition Tool 'connect_material_property' connects an expression to a material output property, which modifies material definitions in the Unreal Engine project.
Attacks that exploit this kind of access
The rule that runs connect_material_property 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 connect_material_property, this is the rule to start with:
connect_material_property 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.
The button opens the PolicyLayer dashboard: create your workspace, connect Unreal, apply this rule, and every connect_material_property call is checked against it from then on.
Questions about connect_material_property
Connect an expression to a material output property (BaseColor, Normal, Metallic, Roughness, etc.). 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.
connect_material_property accepts 4 parameters: output_name, material_path, expression_name, material_property. Required: material_path, expression_name, material_property. The full parameter table on this page comes from the server's own tool schema.
Register the Unreal MCP server in PolicyLayer and add a rule for connect_material_property: 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.
connect_material_property 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 connect_material_property 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 connect_material_property. 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.
connect_material_property 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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