Unity MCP Server

using System; using System.IO; using MCPForUnity.Editor.Helpers; using Newtonsoft.Json.Linq; using UnityEditor; using UnityEditor.SceneManagement; using UnityEngine; using UnityEngine.SceneManagement; namespace MCPForUnity.Editor.Tools.Prefabs { [McpForUnityTool("manage_prefabs", AutoRegister = false)] /// <summary> /// Tool to manage Unity Prefab stages and create prefabs from GameObjects. /// </summary> public static class ManagePrefabs { private const string SupportedActions = "open_stage, close_stage, save_open_stage, create_from_gameobject"; public static object HandleCommand(JObject @params) { if (@params == null) { return new ErrorResponse("Parameters cannot be null."); } string action = @params["action"]?.ToString()?.ToLowerInvariant(); if (string.IsNullOrEmpty(action)) { return new ErrorResponse($"Action parameter is required. Valid actions are: {SupportedActions}."); } try { switch (action) { case "open_stage": return OpenStage(@params); case "close_stage": return CloseStage(@params); case "save_open_stage": return SaveOpenStage(); case "create_from_gameobject": return CreatePrefabFromGameObject(@params); default: return new ErrorResponse($"Unknown action: '{action}'. Valid actions are: {SupportedActions}."); } } catch (Exception e) { McpLog.Error($"[ManagePrefabs] Action '{action}' failed: {e}"); return new ErrorResponse($"Internal error: {e.Message}"); } } private static object OpenStage(JObject @params) { string prefabPath = @params["prefabPath"]?.ToString(); if (string.IsNullOrEmpty(prefabPath)) { return new ErrorResponse("'prefabPath' parameter is required for open_stage."); } string sanitizedPath = AssetPathUtility.SanitizeAssetPath(prefabPath); GameObject prefabAsset = AssetDatabase.LoadAssetAtPath<GameObject>(sanitizedPath); if (prefabAsset == null) { return new ErrorResponse($"No prefab asset found at path '{sanitizedPath}'."); } string modeValue = @params["mode"]?.ToString(); if (!string.IsNullOrEmpty(modeValue) && !modeValue.Equals(PrefabStage.Mode.InIsolation.ToString(), StringComparison.OrdinalIgnoreCase)) { return new ErrorResponse("Only PrefabStage mode 'InIsolation' is supported at this time."); } PrefabStage stage = PrefabStageUtility.OpenPrefab(sanitizedPath); if (stage == null) { return new ErrorResponse($"Failed to open prefab stage for '{sanitizedPath}'."); } return new SuccessResponse($"Opened prefab stage for '{sanitizedPath}'.", SerializeStage(stage)); } private static object CloseStage(JObject @params) { PrefabStage stage = PrefabStageUtility.GetCurrentPrefabStage(); if (stage == null) { return new SuccessResponse("No prefab stage was open."); } bool saveBeforeClose = @params["saveBeforeClose"]?.ToObject<bool>() ?? false; if (saveBeforeClose && stage.scene.isDirty) { SaveStagePrefab(stage); AssetDatabase.SaveAssets(); } StageUtility.GoToMainStage(); return new SuccessResponse($"Closed prefab stage for '{stage.assetPath}'."); } private static object SaveOpenStage() { PrefabStage stage = PrefabStageUtility.GetCurrentPrefabStage(); if (stage == null) { return new ErrorResponse("No prefab stage is currently open."); } SaveStagePrefab(stage); AssetDatabase.SaveAssets(); return new SuccessResponse($"Saved prefab stage for '{stage.assetPath}'.", SerializeStage(stage)); } private static void SaveStagePrefab(PrefabStage stage) { if (stage?.prefabContentsRoot == null) { throw new InvalidOperationException("Cannot save prefab stage without a prefab root."); } bool saved = PrefabUtility.SaveAsPrefabAsset(stage.prefabContentsRoot, stage.assetPath); if (!saved) { throw new InvalidOperationException($"Failed to save prefab asset at '{stage.assetPath}'."); } } private static object CreatePrefabFromGameObject(JObject @params) { string targetName = @params["target"]?.ToString() ?? @params["name"]?.ToString(); if (string.IsNullOrEmpty(targetName)) { return new ErrorResponse("'target' parameter is required for create_from_gameobject."); } bool includeInactive = @params["searchInactive"]?.ToObject<bool>() ?? false; GameObject sourceObject = FindSceneObjectByName(targetName, includeInactive); if (sourceObject == null) { return new ErrorResponse($"GameObject '{targetName}' not found in the active scene."); } if (PrefabUtility.IsPartOfPrefabAsset(sourceObject)) { return new ErrorResponse( $"GameObject '{sourceObject.name}' is part of a prefab asset. Open the prefab stage to save changes instead." ); } PrefabInstanceStatus status = PrefabUtility.GetPrefabInstanceStatus(sourceObject); if (status != PrefabInstanceStatus.NotAPrefab) { return new ErrorResponse( $"GameObject '{sourceObject.name}' is already linked to an existing prefab instance." ); } string requestedPath = @params["prefabPath"]?.ToString(); if (string.IsNullOrWhiteSpace(requestedPath)) { return new ErrorResponse("'prefabPath' parameter is required for create_from_gameobject."); } string sanitizedPath = AssetPathUtility.SanitizeAssetPath(requestedPath); if (!sanitizedPath.EndsWith(".prefab", StringComparison.OrdinalIgnoreCase)) { sanitizedPath += ".prefab"; } bool allowOverwrite = @params["allowOverwrite"]?.ToObject<bool>() ?? false; string finalPath = sanitizedPath; if (!allowOverwrite && AssetDatabase.LoadAssetAtPath<UnityEngine.Object>(finalPath) != null) { finalPath = AssetDatabase.GenerateUniqueAssetPath(finalPath); } EnsureAssetDirectoryExists(finalPath); try { GameObject connectedInstance = PrefabUtility.SaveAsPrefabAssetAndConnect( sourceObject, finalPath, InteractionMode.AutomatedAction ); if (connectedInstance == null) { return new ErrorResponse($"Failed to save prefab asset at '{finalPath}'."); } Selection.activeGameObject = connectedInstance; return new SuccessResponse( $"Prefab created at '{finalPath}' and instance linked.", new { prefabPath = finalPath, instanceId = connectedInstance.GetInstanceID() } ); } catch (Exception e) { return new ErrorResponse($"Error saving prefab asset at '{finalPath}': {e.Message}"); } } private static void EnsureAssetDirectoryExists(string assetPath) { string directory = Path.GetDirectoryName(assetPath); if (string.IsNullOrEmpty(directory)) { return; } string fullDirectory = Path.Combine(Directory.GetCurrentDirectory(), directory); if (!Directory.Exists(fullDirectory)) { Directory.CreateDirectory(fullDirectory); AssetDatabase.Refresh(); } } private static GameObject FindSceneObjectByName(string name, bool includeInactive) { PrefabStage stage = PrefabStageUtility.GetCurrentPrefabStage(); if (stage?.prefabContentsRoot != null) { foreach (Transform transform in stage.prefabContentsRoot.GetComponentsInChildren<Transform>(includeInactive)) { if (transform.name == name) { return transform.gameObject; } } } Scene activeScene = SceneManager.GetActiveScene(); foreach (GameObject root in activeScene.GetRootGameObjects()) { foreach (Transform transform in root.GetComponentsInChildren<Transform>(includeInactive)) { GameObject candidate = transform.gameObject; if (candidate.name == name) { return candidate; } } } return null; } private static object SerializeStage(PrefabStage stage) { if (stage == null) { return new { isOpen = false }; } return new { isOpen = true, assetPath = stage.assetPath, prefabRootName = stage.prefabContentsRoot != null ? stage.prefabContentsRoot.name : null, mode = stage.mode.ToString(), isDirty = stage.scene.isDirty }; } } }