# add_material_expression

A write tool on the Unreal-MCP MCP server.

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

## Facts

- Tool: `add_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: Write (Medium risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Rate-limited

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

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

## Why add_material_expression is rated Medium

This tool creates or modifies material expressions in Unreal Engine, which is a reversible operation (expressions can be deleted or replaced). It does not execute arbitrary code, delete data irreversibly, or move money. The 'add' prefix and material domain context indicate Write category.

From the tool's own definition: "Tool name is 'add_material_expression' which indicates creation/addition of a material expression node in Unreal Engine materials. Sibling tools like 'add_blueprint_node', 'add_component_to_blueprint', 'add_data_table_row' are all additive/creation operations."

## Use case

AI agents use add_material_expression to create or update resources in Unreal-MCP, usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Unreal-MCP environment.

## Recommended policy (PolicyLayer)

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

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "add_material_expression": {
      "limits": [
        {
          "counter": "add_material_expression_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}
```

## 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_material_expression` — Destructive — https://policylayer.com/tools/aadeshrao123-unreal-mcp/delete-material-expression.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
- …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`

---

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