# create_material_instance

Create a material instance from a parent material.

Agent View of the PolicyLayer registry record for `create_material_instance`. HTML page: https://policylayer.com/tools/jjpxdev-unreal-mcp/create-material-instance

## Facts

- Tool: `create_material_instance`
- Server: Unreal (`@jjpxdev/unreal-mcp`) — https://policylayer.com/tools/jjpxdev-unreal-mcp.md
- Install: `npx -y @jjpxdev/unreal-mcp`
- Homepage: https://www.npmjs.com/package/@jjpxdev/unreal-mcp
- Risk category: Write (Medium risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 3 (2 required)
- Recommended policy verdict: Rate-limited

## Parameters

| Parameter | Type | Required | Description |
| --- | --- | --- | --- |
| `name` | string | yes | Material instance name |
| `path` | string | no | Content directory |
| `parent_path` | string | yes | Parent material asset path |

Parameters from the server's own tool schema.

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

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "create_material_instance",
    "arguments": {
      "name": "<name>",
      "parent_path": "<parent_path>"
    }
  }
}
```

## Why create_material_instance is rated Medium

This tool creates a new material instance asset, which is a reversible modification to the project state. Material instances can be deleted or replaced, making this a Write operation rather than Destructive. The severity is medium because creating unwanted materials could clutter the project and consume resources, but the impact is bounded and reversible.

From the tool's own definition: "Tool name 'create_material_instance' and description 'Create a material instance from a parent material' indicate creation of a new asset/resource in Unreal Engine."

Risk signals: Accepts file system path (path)

## Use case

AI agents use create_material_instance 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.

## Recommended policy (PolicyLayer)

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

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

## Other tools on Unreal (126)

- `delete_actor` — Destructive — https://policylayer.com/tools/jjpxdev-unreal-mcp/delete-actor.md
- `delete_asset` — Destructive — https://policylayer.com/tools/jjpxdev-unreal-mcp/delete-asset.md
- `delete_material_expression` — Destructive — https://policylayer.com/tools/jjpxdev-unreal-mcp/delete-material-expression.md
- `remove_graph_node` — Destructive — https://policylayer.com/tools/jjpxdev-unreal-mcp/remove-graph-node.md
- `build_cook_run` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/build-cook-run.md
- `build_graph` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/build-graph.md
- `build_plugin` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/build-plugin.md
- `build_target` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/build-target.md
- `call_preset_function` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/call-preset-function.md
- `clean_project` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/clean-project.md
- `compile_blueprint` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/compile-blueprint.md
- `content_audit` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/content-audit.md
- `cook_content` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/cook-content.md
- `execute_console_command` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/execute-console-command.md
- `execute_python` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/execute-python.md
- `generate_lods` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/generate-lods.md
- `package_project` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/package-project.md
- `recompile_material` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/recompile-material.md
- `reinit_niagara_system` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/reinit-niagara-system.md
- `render_sequence` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/render-sequence.md
- `reset_niagara_system` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/reset-niagara-system.md
- `run_all_automation_tests` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/run-all-automation-tests.md
- `run_automation_test` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/run-automation-test.md
- `run_automation_tests_by_category` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/run-automation-tests-by-category.md
- `run_editor_utility_blueprint` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/run-editor-utility-blueprint.md
- `run_editor_utility_widget` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/run-editor-utility-widget.md
- `run_gauntlet` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/run-gauntlet.md
- `run_map_check` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/run-map-check.md
- `run_stat_command` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/run-stat-command.md
- `spawn_niagara_at_location` — Execute — https://policylayer.com/tools/jjpxdev-unreal-mcp/spawn-niagara-at-location.md
- …and 96 more: https://policylayer.com/tools/jjpxdev-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=jjpxdev-unreal-mcp · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/jjpxdev-unreal-mcp