diff --git a/src/demo/java/io/github/sashirestela/openai/demo/ConversationV2Demo.java b/src/demo/java/io/github/sashirestela/openai/demo/ConversationV2Demo.java
index 175e26c..e044054 100644
--- a/src/demo/java/io/github/sashirestela/openai/demo/ConversationV2Demo.java
+++ b/src/demo/java/io/github/sashirestela/openai/demo/ConversationV2Demo.java
@@ -80,7 +80,7 @@ public void prepareConversation() {
                         .name("World Assistant")
                         .model("gpt-4-turbo")
                         .instructions("You are a skilled tutor on geo-politic topics.")
-                        .tools(AssistantTool.functions(functionList))
+                        .tools(functionExecutor.getToolFunctions())
                         .tool(AssistantTool.FILE_SEARCH)
                         .toolResources(ToolResourceFull.builder()
                                 .fileSearch(FileSearch.builder()
diff --git a/src/demo/java/io/github/sashirestela/openai/demo/ThreadRunStepV2Demo.java b/src/demo/java/io/github/sashirestela/openai/demo/ThreadRunStepV2Demo.java
index 89aa625..5ffec94 100644
--- a/src/demo/java/io/github/sashirestela/openai/demo/ThreadRunStepV2Demo.java
+++ b/src/demo/java/io/github/sashirestela/openai/demo/ThreadRunStepV2Demo.java
@@ -6,7 +6,6 @@
 import io.github.sashirestela.openai.demo.ThreadRunV2Demo.CurrentTemperature;
 import io.github.sashirestela.openai.demo.ThreadRunV2Demo.RainProbability;
 import io.github.sashirestela.openai.domain.assistant.AssistantRequest;
-import io.github.sashirestela.openai.domain.assistant.AssistantTool;
 import io.github.sashirestela.openai.domain.assistant.ThreadMessageRequest;
 import io.github.sashirestela.openai.domain.assistant.ThreadMessageRole;
 import io.github.sashirestela.openai.domain.assistant.ThreadRunRequest;
@@ -45,7 +44,7 @@ private void prepareDemo() {
                         .instructions("You are a very kind assistant. If you cannot find correct facts to answer the "
                                 + "questions, you have to refer to the attached files or use the functions provided. "
                                 + "Finally, if you receive math questions, you must write and run code to answer them.")
-                        .tools(AssistantTool.functions(functionList))
+                        .tools(functionExecutor.getToolFunctions())
                         .temperature(0.2)
                         .build())
                 .join();
diff --git a/src/demo/java/io/github/sashirestela/openai/demo/ThreadRunV2Demo.java b/src/demo/java/io/github/sashirestela/openai/demo/ThreadRunV2Demo.java
index 2f6d7e3..7ab74d7 100644
--- a/src/demo/java/io/github/sashirestela/openai/demo/ThreadRunV2Demo.java
+++ b/src/demo/java/io/github/sashirestela/openai/demo/ThreadRunV2Demo.java
@@ -71,7 +71,7 @@ private void prepareDemo() {
                         .instructions("You are a very kind assistant. If you cannot find correct facts to answer the "
                                 + "questions, you have to refer to the attached files or use the functions provided. "
                                 + "Finally, if you receive math questions, you must write and run code to answer them.")
-                        .tools(AssistantTool.functions(functionList))
+                        .tools(functionExecutor.getToolFunctions())
                         .tool(AssistantTool.FILE_SEARCH)
                         .toolResources(ToolResourceFull.builder()
                                 .fileSearch(FileSearch.builder()
diff --git a/src/main/java/io/github/sashirestela/openai/common/tool/Tool.java b/src/main/java/io/github/sashirestela/openai/common/tool/Tool.java
index c607ca4..79134fc 100644
--- a/src/main/java/io/github/sashirestela/openai/common/tool/Tool.java
+++ b/src/main/java/io/github/sashirestela/openai/common/tool/Tool.java
@@ -12,9 +12,6 @@
 import lombok.NoArgsConstructor;
 import lombok.ToString;
 
-import java.util.List;
-import java.util.stream.Collectors;
-
 @AllArgsConstructor
 @NoArgsConstructor
 @Getter
@@ -33,12 +30,6 @@ public static Tool function(FunctionDef function) {
                         JsonSchemaUtil.classToJsonSchema(function.getFunctionalClass())));
     }
 
-    public static List<Tool> functions(List<FunctionDef> functions) {
-        return functions.stream()
-                .map(funDef -> function(funDef))
-                .collect(Collectors.toList());
-    }
-
     @AllArgsConstructor(access = AccessLevel.PROTECTED)
     @NoArgsConstructor
     @Getter
diff --git a/src/main/java/io/github/sashirestela/openai/domain/assistant/Assistant.java b/src/main/java/io/github/sashirestela/openai/domain/assistant/Assistant.java
index 1c8afee..f9ef5b6 100644
--- a/src/main/java/io/github/sashirestela/openai/domain/assistant/Assistant.java
+++ b/src/main/java/io/github/sashirestela/openai/domain/assistant/Assistant.java
@@ -2,6 +2,7 @@
 
 import com.fasterxml.jackson.databind.PropertyNamingStrategies;
 import com.fasterxml.jackson.databind.annotation.JsonNaming;
+import io.github.sashirestela.openai.common.tool.Tool;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
 import lombok.ToString;
@@ -22,7 +23,7 @@ public class Assistant {
     private String description;
     private String model;
     private String instructions;
-    private List<AssistantTool> tools;
+    private List<Tool> tools;
     private ToolResource toolResources;
     private Map<String, String> metadata;
     private Double temperature;
diff --git a/src/main/java/io/github/sashirestela/openai/domain/assistant/AssistantModifyRequest.java b/src/main/java/io/github/sashirestela/openai/domain/assistant/AssistantModifyRequest.java
index 540029e..a0cb020 100644
--- a/src/main/java/io/github/sashirestela/openai/domain/assistant/AssistantModifyRequest.java
+++ b/src/main/java/io/github/sashirestela/openai/domain/assistant/AssistantModifyRequest.java
@@ -5,6 +5,7 @@
 import com.fasterxml.jackson.databind.PropertyNamingStrategies;
 import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import io.github.sashirestela.openai.common.ResponseFormat;
+import io.github.sashirestela.openai.common.tool.Tool;
 import io.github.sashirestela.slimvalidator.constraints.ObjectType;
 import io.github.sashirestela.slimvalidator.constraints.Range;
 import io.github.sashirestela.slimvalidator.constraints.Size;
@@ -34,7 +35,7 @@ public class AssistantModifyRequest {
 
     @Singular
     @Size(max = 128)
-    private List<AssistantTool> tools;
+    private List<Tool> tools;
 
     private ToolResource toolResources;
 
diff --git a/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadCreateAndRunRequest.java b/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadCreateAndRunRequest.java
index 9cae449..1ccc341 100644
--- a/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadCreateAndRunRequest.java
+++ b/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadCreateAndRunRequest.java
@@ -4,6 +4,7 @@
 import com.fasterxml.jackson.databind.PropertyNamingStrategies;
 import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import io.github.sashirestela.openai.common.ResponseFormat;
+import io.github.sashirestela.openai.common.tool.Tool;
 import io.github.sashirestela.openai.common.tool.ToolChoice;
 import io.github.sashirestela.openai.common.tool.ToolChoiceOption;
 import io.github.sashirestela.slimvalidator.constraints.ObjectType;
@@ -34,7 +35,7 @@ public class ThreadCreateAndRunRequest {
     private String instructions;
     @Singular
     @Size(max = 20)
-    private List<AssistantTool> tools;
+    private List<Tool> tools;
 
     private ToolResource toolResources;
 
diff --git a/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadRun.java b/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadRun.java
index ce291eb..4c44acd 100644
--- a/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadRun.java
+++ b/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadRun.java
@@ -4,6 +4,7 @@
 import com.fasterxml.jackson.databind.PropertyNamingStrategies;
 import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import io.github.sashirestela.openai.common.Usage;
+import io.github.sashirestela.openai.common.tool.Tool;
 import io.github.sashirestela.openai.common.tool.ToolCall;
 import lombok.Getter;
 import lombok.NoArgsConstructor;
@@ -34,7 +35,7 @@ public class ThreadRun {
     private IncompleteDetail incompleteDetails;
     private String model;
     private String instructions;
-    private List<AssistantTool> tools;
+    private List<Tool> tools;
     private Map<String, String> metadata;
     private Usage usage;
     private Double temperature;
diff --git a/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadRunRequest.java b/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadRunRequest.java
index be47052..5797f0a 100644
--- a/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadRunRequest.java
+++ b/src/main/java/io/github/sashirestela/openai/domain/assistant/ThreadRunRequest.java
@@ -4,6 +4,7 @@
 import com.fasterxml.jackson.databind.PropertyNamingStrategies;
 import com.fasterxml.jackson.databind.annotation.JsonNaming;
 import io.github.sashirestela.openai.common.ResponseFormat;
+import io.github.sashirestela.openai.common.tool.Tool;
 import io.github.sashirestela.openai.common.tool.ToolChoice;
 import io.github.sashirestela.openai.common.tool.ToolChoiceOption;
 import io.github.sashirestela.slimvalidator.constraints.ObjectType;
@@ -38,7 +39,7 @@ public class ThreadRunRequest {
 
     @Singular
     @Size(max = 20)
-    private List<AssistantTool> tools;
+    private List<Tool> tools;
 
     @Size(max = 16)
     private Map<String, String> metadata;