Remove an expression node from a material graph.
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.
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
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.
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 (sam-david/unreal-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
delete_material_expression is one line of Unreal's registry record.
The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.
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