# delete_material_expression

Delete a single expression node by index. Recompiles and saves automatically.

Agent View of the PolicyLayer registry record for `delete_material_expression`. HTML page: https://policylayer.com/tools/aadeshrao123-unreal-mcp/delete-material-expression

## Facts

- Tool: `delete_material_expression`
- Server: Unreal-MCP (`aadeshrao123/unreal-mcp`) — https://policylayer.com/tools/aadeshrao123-unreal-mcp.md
- Homepage: https://github.com/aadeshrao123/Unreal-MCP
- Risk category: Destructive (Critical risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Hidden

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "delete_material_expression",
    "arguments": {}
  }
}
```

## Why delete_material_expression is rated Critical

The tool irreversibly deletes material expression nodes in the Unreal Engine editor. The deletion is automatic, persistent (saves immediately), and cannot be undone programmatically by the tool itself. This fits the Destructive category as it removes data that would require manual recreation.

From the tool's own definition: "delete_material_expression deletes a single expression node by index. Recompiles and saves automatically."

## Use case

AI agents call delete_material_expression to permanently remove resources in Unreal-MCP, typically in cleanup and lifecycle workflows. It does its job in a single call, and there is no undo.

## Recommended policy (PolicyLayer)

Verdict: **Hidden**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches Unreal-MCP:

```json
{
  "version": "1",
  "default": "deny",
  "hide": [
    "delete_material_expression"
  ]
}
```

## Other tools on Unreal-MCP (285)

- `cleanup_material_function` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/cleanup-material-function.md
- `cleanup_material_graph` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/cleanup-material-graph.md
- `clear_niagara_module_input` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/clear-niagara-module-input.md
- `delete_actor` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/delete-actor.md
- `delete_asset` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/delete-asset.md
- `delete_blueprint_function` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/delete-blueprint-function.md
- `delete_blueprint_node` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/delete-blueprint-node.md
- `delete_data_table_row` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/delete-data-table-row.md
- `delete_niagara_graph_node` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/delete-niagara-graph-node.md
- `delete_niagara_scratch_pad_module` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/delete-niagara-scratch-pad-module.md
- `delete_niagara_system` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/delete-niagara-system.md
- `remove_input_action_modifier` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-input-action-modifier.md
- `remove_input_action_trigger` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-input-action-trigger.md
- `remove_key_mapping` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-key-mapping.md
- `remove_mapping_modifier` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-mapping-modifier.md
- `remove_mapping_trigger` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-mapping-trigger.md
- `remove_mass_config_trait` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-mass-config-trait.md
- `remove_niagara_custom_hlsl_pin` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-niagara-custom-hlsl-pin.md
- `remove_niagara_emitter` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-niagara-emitter.md
- `remove_niagara_module` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-niagara-module.md
- `remove_niagara_node_pin` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-niagara-node-pin.md
- `remove_niagara_renderer` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-niagara-renderer.md
- `remove_niagara_script_parameter` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-niagara-script-parameter.md
- `remove_niagara_user_parameter` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-niagara-user-parameter.md
- `remove_statetree_binding` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-statetree-binding.md
- `remove_statetree_node` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-statetree-node.md
- `remove_statetree_parameter` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-statetree-parameter.md
- `remove_statetree_state` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-statetree-state.md
- `remove_statetree_transition` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-statetree-transition.md
- `remove_widget` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/remove-widget.md
- …and 255 more: https://policylayer.com/tools/aadeshrao123-unreal-mcp.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

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Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=aadeshrao123-unreal-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/aadeshrao123-unreal-mcp