Our review

Opens Unity prefab edit mode for a scene instance or asset GameObject, allowing changes to the prefab to propagate to all its instances.

Strengths

Edit a prefab directly from a scene instance
Uses PrefabUtility to resolve the prefab asset path automatically
Supports multiple reference types (instanceID, path, name, GUID)

Limitations

Requires a resolvable GameObject and accessible prefab
Must be followed by assets-prefab-close to exit edit mode
Returns no structured output
Only works in a Unity environment with the unity-mcp-cli package configured

When to use it

When you need to edit a Unity prefab and have the changes apply to all its instances from an AI agent.

When not to use it

When the change should stay local to one scene instance without affecting other instances.

Examples

Open prefab from selected instance

Open the prefab edit stage for the currently selected GameObject in the scene.

Edit prefab asset by path

Open the prefab stage for Assets/Characters/Player.prefab so I can rename its child objects.

Tweak prefab by instance name

Open prefab editing for the 'Enemy_Door' instance found in the scene.

name: assets-prefab-open description: Open the prefab edit stage for a prefab instance or prefab asset GameObject. Modifications inside the edit stage propagate to all instances. Pair with 'assets-prefab-close' to exit the stage when done.

Assets / Prefab / Open

Open prefab edit mode for a specific GameObject. In the Edit mode you can modify the prefab. The modification will be applied to all instances of the prefab across the project. Note: Please use 'assets-prefab-close' tool later to exit prefab editing mode.

Inputs

gameObjectRef — reference to a scene prefab instance OR a prefab asset GameObject. The tool resolves the prefab asset path via PrefabUtility.GetPrefabAssetPathOfNearestInstanceRoot and opens the appropriate prefab stage.

Behavior

Asset-side GameObjects open via the simple OpenPrefab(path) overload. Scene-instance GameObjects open via OpenPrefab(path, gameObject) so the editor remembers which instance prompted the edit. Editor windows are repainted before returning. Throws when the GameObject cannot be resolved or the stage fails to open.

How to Call

unity-mcp-cli run-tool assets-prefab-open --input '{
  "gameObjectRef": "string_value"
}'

For complex input (multi-line strings, code), save the JSON to a file and use:
unity-mcp-cli run-tool assets-prefab-open --input-file args.json
Or pipe via stdin (recommended):
unity-mcp-cli run-tool assets-prefab-open --input-file - <<'EOF'
{"param": "value"}
EOF

Troubleshooting

If unity-mcp-cli is not found, either install it globally (npm install -g unity-mcp-cli) or use npx unity-mcp-cli instead. Read the /unity-initial-setup skill for detailed installation instructions.

Input

| Name | Type | Required | Description | |------|------|----------|-------------| | gameObjectRef | any | Yes | GameObject that represents prefab instance of an original prefab GameObject. |

Input JSON Schema

{
  "type": "object",
  "properties": {
    "gameObjectRef": {
      "$ref": "#/$defs/AIGD.GameObjectRef"
    }
  },
  "$defs": {
    "System.Type": {
      "type": "string"
    },
    "AIGD.GameObjectRef": {
      "type": "object",
      "properties": {
        "instanceID": {
          "type": "integer",
          "description": "instanceID of the UnityEngine.Object. If it is '0' and 'path', 'name', 'assetPath' and 'assetGuid' is not provided, empty or null, then it will be used as 'null'. Priority: 1 (Recommended)"
        },
        "path": {
          "type": "string",
          "description": "Path of a GameObject in the hierarchy Sample 'character/hand/finger/particle'. Priority: 2."
        },
        "name": {
          "type": "string",
          "description": "Name of a GameObject in hierarchy. Priority: 3."
        },
        "assetType": {
          "$ref": "#/$defs/System.Type",
          "description": "Type of the asset."
        },
        "assetPath": {
          "type": "string",
          "description": "Path to the asset within the project. Starts with 'Assets/'"
        },
        "assetGuid": {
          "type": "string",
          "description": "Unique identifier for the asset."
        }
      },
      "required": [
        "instanceID"
      ],
      "description": "Find GameObject in opened Prefab or in the active Scene."
    }
  },
  "required": [
    "gameObjectRef"
  ]
}

Output

This tool does not return structured output.

Open Prefab Edit Mode

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