connect_material_expressions
Wire two material expression nodes together.
This record as markdown: /tools/jjpxdev-unreal-mcp/connect-material-expressions.md
What connect_material_expressions does on Unreal
AI agents use connect_material_expressions 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 |
|---|---|---|---|
material_path | string | Yes | Material asset path |
to_input_name | string | — | Target input pin name (empty string for first/default input) |
from_output_name | string | — | Source output pin name (empty string for first/default output) |
to_expression_name | string | Yes | Target expression name |
from_expression_name | string | Yes | Source expression name |
Parameters from the server's own tool schema.
Why connect_material_expressions is rated Medium
The tool modifies the material expression graph by establishing connections between nodes, which is a Write operation—creating/modifying data structures. While this can affect rendering output, the changes are reversible (connections can be unwired) and do not constitute Destructive operations.
From the tool's definition Tool name 'connect_material_expressions' and description 'Wire two material expression nodes together' indicate modification of material node graphs in Unreal Engine. This is a reversible graph editing operation that creates connections between nodes.
Attacks that exploit this kind of access
The rule that runs connect_material_expressions 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_expressions, this is the rule to start with:
connect_material_expressions 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_expressions call is checked against it from then on.
Questions about connect_material_expressions
Wire two material expression nodes together. 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_expressions accepts 5 parameters: material_path, to_input_name, from_output_name, to_expression_name, from_expression_name. Required: material_path, to_expression_name, from_expression_name. 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_expressions: 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_expressions 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_expressions 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_expressions. 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_expressions 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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