diff --git a/core/deployment/src/main/java/io/quarkiverse/langchain4j/deployment/ToolProcessor.java b/core/deployment/src/main/java/io/quarkiverse/langchain4j/deployment/ToolProcessor.java
index a3405eb93..47220e7a6 100644
--- a/core/deployment/src/main/java/io/quarkiverse/langchain4j/deployment/ToolProcessor.java
+++ b/core/deployment/src/main/java/io/quarkiverse/langchain4j/deployment/ToolProcessor.java
@@ -292,7 +292,7 @@ private static String generateInvoker(MethodInfo methodInfo, ClassOutput classOu
 
             boolean toolReturnsVoid = methodInfo.returnType().kind() == Type.Kind.VOID;
             if (toolReturnsVoid) {
-                invokeMc.returnValue(invokeMc.load("Success"));
+                invokeMc.returnValue(invokeMc.load("\"Success\""));
             } else {
                 invokeMc.returnValue(result);
             }
diff --git a/core/runtime/src/main/java/io/quarkiverse/langchain4j/runtime/tool/QuarkusToolExecutor.java b/core/runtime/src/main/java/io/quarkiverse/langchain4j/runtime/tool/QuarkusToolExecutor.java
index 126ea21a5..d8cb88c36 100644
--- a/core/runtime/src/main/java/io/quarkiverse/langchain4j/runtime/tool/QuarkusToolExecutor.java
+++ b/core/runtime/src/main/java/io/quarkiverse/langchain4j/runtime/tool/QuarkusToolExecutor.java
@@ -61,7 +61,7 @@ public String execute(ToolExecutionRequest toolExecutionRequest, Object memoryId
 
     private static String handleResult(ToolInvoker invokerInstance, Object invocationResult) {
         if (invokerInstance.methodMetadata().isReturnsVoid()) {
-            return "Success";
+            return "\"Success\"";
         }
         return Json.toJson(invocationResult);
     }