More MCP refactoring

Plugins/BlueprintMCP/Source/BlueprintMCP/Private/MCPHandlers_AnimMutation.h

@@ -332,6 +332,21 @@ public:
 // ---------------------------------------------------------------------------
 // ---------------------------------------------------------------------------
 
+USTRUCT()
+struct FBlendSpaceSampleEntry
+{
+	GENERATED_BODY()
+
+	UPROPERTY()
+	FString AnimationAsset;
+
+	UPROPERTY()
+	float X = 0.0f;
+
+	UPROPERTY()
+	float Y = 0.0f;
+};
+
 UCLASS(meta=(ToolName="set_blend_space_sample_points"))
 class UMCPHandler_SetBlendSpaceSamples : public UObject, public IMCPHandler
 {
@@ -410,22 +425,18 @@ public:
 
 		for (const TSharedPtr<FJsonValue>& SampleVal : Samples.Array)
 		{
-			const TSharedPtr<FJsonObject>& SampleObj = SampleVal->AsObject();
+			FBlendSpaceSampleEntry Entry;
-			if (!SampleObj.IsValid()) continue;
+			if (!MCPUtils::PopulateFromJson(FBlendSpaceSampleEntry::StaticStruct(), &Entry, SampleVal, Result)) return;
-
-			FString AnimAssetName = SampleObj->GetStringField(TEXT("animationAsset"));
-			float X = (float)SampleObj->GetNumberField(TEXT("x"));
-			float Y = (float)SampleObj->GetNumberField(TEXT("y"));
 
 			UAnimSequence* AnimSeq = nullptr;
-			if (!AnimAssetName.IsEmpty())
+			if (!Entry.AnimationAsset.IsEmpty())
 			{
 				MCPAssets<UAnimSequence> AnimAssets;
-				if (AnimAssets.Exact(AnimAssetName).Load())
+				if (AnimAssets.Exact(Entry.AnimationAsset).Load())
 					AnimSeq = AnimAssets.Object();
 			}
 
-			FVector SampleValue(X, Y, 0.0f);
+			FVector SampleValue(Entry.X, Entry.Y, 0.0f);
 			if (AnimSeq)
 			{
 				BS->AddSample(AnimSeq, SampleValue);

Plugins/BlueprintMCP/Source/BlueprintMCP/Private/MCPHandlers_Dispatchers.h

@@ -16,6 +16,18 @@
 // ---------------------------------------------------------------------------
 // ---------------------------------------------------------------------------
 
+USTRUCT()
+struct FDispatcherParamEntry
+{
+	GENERATED_BODY()
+
+	UPROPERTY()
+	FString Name;
+
+	UPROPERTY()
+	FString Type;
+};
+
 UCLASS(meta=(ToolName="add_event_dispatcher"))
 class UMCPHandler_AddEventDispatcher : public UObject, public IMCPHandler
 {
@@ -117,23 +129,19 @@ public:
 
 			for (const TSharedPtr<FJsonValue>& ParamVal : Parameters.Array)
 			{
-				if (!ParamVal.IsValid() || ParamVal->Type != EJson::Object) continue;
+				FDispatcherParamEntry Entry;
-				TSharedPtr<FJsonObject> ParamObj = ParamVal->AsObject();
+				if (!MCPUtils::PopulateFromJson(FDispatcherParamEntry::StaticStruct(), &Entry, ParamVal, Result)) return;
-
+				if (Entry.Name.IsEmpty() || Entry.Type.IsEmpty()) continue;
-				FString ParamName = ParamObj->GetStringField(TEXT("name"));
-				FString ParamType = ParamObj->GetStringField(TEXT("type"));
-
-				if (ParamName.IsEmpty() || ParamType.IsEmpty()) continue;
 
 				FEdGraphPinType PinType;
-				if (!MCPUtils::ResolveTypeFromString(ParamType, PinType, Result))
+				if (!MCPUtils::ResolveTypeFromString(Entry.Type, PinType, Result))
 					return;
 
-				EntryNode->CreateUserDefinedPin(FName(*ParamName), PinType, EGPD_Output);
+				EntryNode->CreateUserDefinedPin(FName(*Entry.Name), PinType, EGPD_Output);
 
 				TSharedRef<FJsonObject> ParamJson = MakeShared<FJsonObject>();
-				ParamJson->SetStringField(TEXT("name"), ParamName);
+				ParamJson->SetStringField(TEXT("name"), Entry.Name);
-				ParamJson->SetStringField(TEXT("type"), ParamType);
+				ParamJson->SetStringField(TEXT("type"), Entry.Type);
 				AddedParamsJson.Add(MakeShared<FJsonValueObject>(ParamJson));
 			}
 		}

Plugins/BlueprintMCP/Source/BlueprintMCP/Private/MCPHandlers_Mutation.h

@@ -103,12 +103,7 @@ public:
 			Results.Add(MakeShared<FJsonValueObject>(EntryResult));
 
 			FMoveNodeEntry Entry;
-			FString PopulateError = MCPUtils::PopulateFromJson(FMoveNodeEntry::StaticStruct(), &Entry, NodeVal);
+			if (!MCPUtils::PopulateFromJson(FMoveNodeEntry::StaticStruct(), &Entry, NodeVal, &*EntryResult)) continue;
-			if (!PopulateError.IsEmpty())
-			{
-				EntryResult->SetStringField(TEXT("error"), PopulateError);
-				continue;
-			}
 
 			UEdGraphNode* Node = MCPUtils::FindNodeByGuid(BP, Entry.Node);
 			if (!Node)
@@ -362,12 +357,7 @@ public:
 			Results.Add(MakeShared<FJsonValueObject>(EntryResult));
 
 			FSpawnNodeEntry Entry;
-			FString PopulateError = MCPUtils::PopulateFromJson(FSpawnNodeEntry::StaticStruct(), &Entry, NodeVal);
+			if (!MCPUtils::PopulateFromJson(FSpawnNodeEntry::StaticStruct(), &Entry, NodeVal, &*EntryResult)) continue;
-			if (!PopulateError.IsEmpty())
-			{
-				EntryResult->SetStringField(TEXT("error"), PopulateError);
-				continue;
-			}
 
 			// Find the spawner by exact full name
 			TArray<UBlueprintNodeSpawner*> Matches = MCPUtils::SearchNodeSpawners(Entry.ActionName, 0, /*ExactMatch=*/true, TargetGraph);

Plugins/BlueprintMCP/Source/BlueprintMCP/Private/MCPHandlers_PinMutation.h

@@ -63,12 +63,7 @@ public:
 			Results.Add(MakeShared<FJsonValueObject>(EntryResult));
 
 			FSetPinDefaultEntry Entry;
-			FString PopulateError = MCPUtils::PopulateFromJson(FSetPinDefaultEntry::StaticStruct(), &Entry, PinVal);
+			if (!MCPUtils::PopulateFromJson(FSetPinDefaultEntry::StaticStruct(), &Entry, PinVal, &*EntryResult)) continue;
-			if (!PopulateError.IsEmpty())
-			{
-				EntryResult->SetStringField(TEXT("error"), PopulateError);
-				continue;
-			}
 
 			MCPAssets<UBlueprint> Assets;
 			if (!Assets.Scan<UBlueprint>().Scan<UWorld>().Exact(Entry.Blueprint).Errors(&*EntryResult).ENone().ETwo().Load())
@@ -192,12 +187,7 @@ public:
 			Results.Add(MakeShared<FJsonValueObject>(EntryResult));
 
 			FConnectPinsEntry Entry;
-			FString PopulateError = MCPUtils::PopulateFromJson(FConnectPinsEntry::StaticStruct(), &Entry, ConnVal);
+			if (!MCPUtils::PopulateFromJson(FConnectPinsEntry::StaticStruct(), &Entry, ConnVal, &*EntryResult)) continue;
-			if (!PopulateError.IsEmpty())
-			{
-				EntryResult->SetStringField(TEXT("error"), PopulateError);
-				continue;
-			}
 
 			UEdGraph* SourceGraph = nullptr;
 			UEdGraphNode* SourceNode = MCPUtils::FindNodeByGuid(BP, Entry.SourceNode, &SourceGraph);
@@ -319,12 +309,7 @@ public:
 			Results.Add(MakeShared<FJsonValueObject>(EntryResult));
 
 			FDisconnectPinEntry Entry;
-			FString PopulateError = MCPUtils::PopulateFromJson(FDisconnectPinEntry::StaticStruct(), &Entry, DiscVal);
+			if (!MCPUtils::PopulateFromJson(FDisconnectPinEntry::StaticStruct(), &Entry, DiscVal, &*EntryResult)) continue;
-			if (!PopulateError.IsEmpty())
-			{
-				EntryResult->SetStringField(TEXT("error"), PopulateError);
-				continue;
-			}
 
 			UEdGraphNode* Node = MCPUtils::FindNodeByGuid(BP, Entry.Node);
 			if (!Node)

Plugins/BlueprintMCP/Source/BlueprintMCP/Private/MCPHandlers_UserTypes.h

@@ -21,6 +21,18 @@
 // ---------------------------------------------------------------------------
 // ---------------------------------------------------------------------------
 
+USTRUCT()
+struct FStructPropertyEntry
+{
+	GENERATED_BODY()
+
+	UPROPERTY()
+	FString Name;
+
+	UPROPERTY()
+	FString Type;
+};
+
 UCLASS(meta=(ToolName="create_struct_asset"))
 class UMCPHandler_CreateStruct : public UObject, public IMCPHandler
 {
@@ -77,18 +89,15 @@ public:
     	int32 PropsAdded = 0;
     	for (const TSharedPtr<FJsonValue>& PropVal : Properties.Array)
     	{
-    		TSharedPtr<FJsonObject> PropObj = PropVal->AsObject();
+    		FStructPropertyEntry Entry;
-    		if (!PropObj) continue;
+    		if (!MCPUtils::PopulateFromJson(FStructPropertyEntry::StaticStruct(), &Entry, PropVal, Result)) return;
-
+    		if (Entry.Name.IsEmpty() || Entry.Type.IsEmpty()) continue;
-    		FString PropName = PropObj->GetStringField(TEXT("name"));
-    		FString PropType = PropObj->GetStringField(TEXT("type"));
-    		if (PropName.IsEmpty() || PropType.IsEmpty()) continue;
 
     		FEdGraphPinType PinType;
     		FString TypeError;
-    		if (!MCPUtils::ResolveTypeFromString(PropType, PinType, TypeError))
+    		if (!MCPUtils::ResolveTypeFromString(Entry.Type, PinType, TypeError))
     		{
-    			UE_LOG(LogTemp, Warning, TEXT("BlueprintMCP: Could not resolve type '%s' for property '%s': %s"), *PropType, *PropName, *TypeError);
+    			UE_LOG(LogTemp, Warning, TEXT("BlueprintMCP: Could not resolve type '%s' for property '%s': %s"), *Entry.Type, *Entry.Name, *TypeError);
     			continue;
     		}
 
@@ -114,7 +123,7 @@ public:
     			}
     			if (NewPropGuid.IsValid())
     			{
-    				FStructureEditorUtils::RenameVariable(NewStruct, NewPropGuid, PropName);
+    				FStructureEditorUtils::RenameVariable(NewStruct, NewPropGuid, Entry.Name);
     			}
     			PropsAdded++;
     		}

Plugins/BlueprintMCP/Source/BlueprintMCP/Private/MCPServer.cpp

@@ -261,15 +261,10 @@ void FMCPServer::DispatchToolCall(const FString& ToolName, const FJsonObject* Pa
 
 		TStrongObjectPtr<UObject> HandlerObj(NewObject<UObject>(GetTransientPackage(), *HandlerClass));
 		IMCPHandler* Handler = Cast<IMCPHandler>(HandlerObj.Get());
-		FString PopulateError = MCPUtils::PopulateFromJson(HandlerObj->GetClass(), HandlerObj.Get(), Params);
+		if (MCPUtils::PopulateFromJson(HandlerObj->GetClass(), HandlerObj.Get(), Params, Result))
-		if (PopulateError.IsEmpty())
 		{
 			Handler->Handle(Params, Result);
 		}
-		else
-		{
-			MCPUtils::MakeErrorJson(Result, PopulateError);
-		}
 
 		if (bIsMutation && GEditor)
 		{

Plugins/BlueprintMCP/Source/BlueprintMCP/Private/MCPUtils.cpp

@@ -1427,22 +1427,25 @@ FString MCPUtils::SetPropertyFromJson(
 		*FieldName, *Prop->GetCPPType());
 }
 
-FString MCPUtils::PopulateFromJson(
+bool MCPUtils::PopulateFromJson(
 	UStruct* StructType,
 	void* Container,
-	const TSharedPtr<FJsonValue>& JsonValue)
+	const TSharedPtr<FJsonValue>& JsonValue,
+	MCPErrorCallback Error)
 {
 	if (!JsonValue.IsValid() || (JsonValue->Type != EJson::Object))
 	{
-		return TEXT("Expected a JSON object");
+		Error.SetError(TEXT("Expected a JSON object"));
+		return false;
 	}
-	return PopulateFromJson(StructType, Container, JsonValue->AsObject().Get());
+	return PopulateFromJson(StructType, Container, JsonValue->AsObject().Get(), Error);
 }
 
-FString MCPUtils::PopulateFromJson(
+bool MCPUtils::PopulateFromJson(
 	UStruct* StructType,
 	void* Container,
-	const FJsonObject* Json)
+	const FJsonObject* Json,
+	MCPErrorCallback Error)
 {
 	// Build a set of known property names (as JSON keys) for the unknown-field check.
 	TSet<FString> KnownKeys;
@@ -1460,7 +1463,8 @@ FString MCPUtils::PopulateFromJson(
 	{
 		if (!KnownKeys.Contains(KV.Key))
 		{
-			return FString::Printf(TEXT("Unknown parameter '%s'"), *KV.Key);
+			Error.SetError(FString::Printf(TEXT("Unknown parameter '%s'"), *KV.Key));
+			return false;
 		}
 	}
 
@@ -1474,17 +1478,19 @@ FString MCPUtils::PopulateFromJson(
 		{
 			if (!bOptional)
 			{
-				return FString::Printf(TEXT("Missing required parameter '%s'"), *JsonKey);
+				Error.SetError(FString::Printf(TEXT("Missing required parameter '%s'"), *JsonKey));
+				return false;
 			}
 			continue;
 		}
 
-		FString Error = SetPropertyFromJson(Container, Prop, JsonKey, Json);
+		FString PropError = SetPropertyFromJson(Container, Prop, JsonKey, Json);
-		if (!Error.IsEmpty())
+		if (!PropError.IsEmpty())
 		{
-			return Error;
+			Error.SetError(PropError);
+			return false;
 		}
 	}
 
-	return FString();
+	return true;
 }

Plugins/BlueprintMCP/Source/BlueprintMCP/Public/MCPUtils.h

@@ -149,8 +149,8 @@ public:
 
 	// ----- Property population -----
 	static FString PropertyNameToJsonKey(const FString& PropName);
-	static FString PopulateFromJson(UStruct* StructType, void* Container, const TSharedPtr<FJsonValue>& JsonValue);
+	static bool PopulateFromJson(UStruct* StructType, void* Container, const TSharedPtr<FJsonValue>& JsonValue, MCPErrorCallback Error);
-	static FString PopulateFromJson(UStruct* StructType, void* Container, const FJsonObject* Json);
+	static bool PopulateFromJson(UStruct* StructType, void* Container, const FJsonObject* Json, MCPErrorCallback Error);
 
 private:
 	static FString SetPropertyFromJson(void* Container, FProperty* Prop, const FString& FieldName, const FJsonObject* Json);