delete_material_expression
Remove an expression node from a material graph.
This record as markdown: /tools/jjpxdev-unreal-mcp/delete-material-expression.md
What delete_material_expression does on Unreal
AI agents call delete_material_expression to permanently remove resources in Unreal, typically in cleanup and lifecycle workflows. It does its job in a single call, and there is no undo.
| Parameter | Type | Required | Description |
|---|---|---|---|
material_path | string | Yes | Material asset path |
expression_name | string | Yes | Expression name to delete |
Parameters from the server's own tool schema.
Why delete_material_expression is rated Critical
This tool deletes a material expression node, which is an irreversible operation that modifies the material graph structure. While the scope is limited to a single node rather than an entire asset or project, deletion of material graph components cannot be undone without undo/redo system support, making it destructive.
From the tool's definition 'Remove an expression node from a material graph' indicates irreversible deletion of a material graph component. The verb 'Remove' combined with 'expression node' confirms destructive action on asset data.
Attacks that exploit this kind of access
The rule that runs delete_material_expression 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 delete_material_expression, this is the rule to start with:
delete_material_expression is removed from the agent's tool list entirely, so the agent never calls it. The rest of the server keeps working.
The button opens the PolicyLayer dashboard: create your workspace, connect Unreal, apply this rule, and every delete_material_expression call is checked against it from then on.
Questions about delete_material_expression
Remove an expression node from a material graph. It is categorised as a Destructive tool in the Unreal MCP Server, which means it can permanently delete or destroy data. Block by default and require explicit approval.
delete_material_expression accepts 2 parameters: material_path, expression_name. Required: material_path, 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 delete_material_expression: 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.
delete_material_expression is a Destructive tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.
Yes. Add a rate_limit block to the delete_material_expression 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 delete_material_expression. 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.
delete_material_expression 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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