diff --git a/src/openai/types/chat/__init__.py b/src/openai/types/chat/__init__.py
index c9e77ff41c..a47e19f288 100644
--- a/src/openai/types/chat/__init__.py
+++ b/src/openai/types/chat/__init__.py
@@ -54,6 +54,7 @@
 )
 from .chat_completion_message_tool_call_param import (
     ChatCompletionMessageToolCallParam as ChatCompletionMessageToolCallParam,
+    ChatCompletionMessageToolCallParamType as ChatCompletionMessageToolCallParamType,
 )
 from .chat_completion_named_tool_choice_param import (
     ChatCompletionNamedToolChoiceParam as ChatCompletionNamedToolChoiceParam,
diff --git a/src/openai/types/chat/chat_completion_message_tool_call_param.py b/src/openai/types/chat/chat_completion_message_tool_call_param.py
index 96ba6521f0..b4311915f3 100644
--- a/src/openai/types/chat/chat_completion_message_tool_call_param.py
+++ b/src/openai/types/chat/chat_completion_message_tool_call_param.py
@@ -2,14 +2,63 @@
 
 from __future__ import annotations
 
-from typing import Union
-from typing_extensions import TypeAlias
+from typing import Any, Union, overload
+from typing_extensions import Literal, TypeAlias
 
-from .chat_completion_message_custom_tool_call_param import ChatCompletionMessageCustomToolCallParam
-from .chat_completion_message_function_tool_call_param import ChatCompletionMessageFunctionToolCallParam
+from .chat_completion_message_custom_tool_call_param import ChatCompletionMessageCustomToolCallParam, Custom
+from .chat_completion_message_function_tool_call_param import ChatCompletionMessageFunctionToolCallParam, Function
 
-__all__ = ["ChatCompletionMessageToolCallParam"]
+__all__ = ["ChatCompletionMessageToolCallParam", "ChatCompletionMessageToolCallParamType"]
 
-ChatCompletionMessageToolCallParam: TypeAlias = Union[
+
+class _ChatCompletionMessageToolCallParamConstructor:
+    """
+    Constructor class that provides backward compatibility for ChatCompletionMessageToolCallParam.
+    This allows instantiation while maintaining the Union type behavior.
+    """
+    
+    @overload
+    def __call__(
+        self,
+        *,
+        id: str,
+        type: Literal["function"],
+        function: Function,
+        **kwargs: Any,
+    ) -> ChatCompletionMessageFunctionToolCallParam: ...
+    
+    @overload  
+    def __call__(
+        self,
+        *,
+        id: str,
+        type: Literal["custom"],
+        custom: Custom,
+        **kwargs: Any,
+    ) -> ChatCompletionMessageCustomToolCallParam: ...
+    
+    def __call__(self, **kwargs: Any) -> Union[ChatCompletionMessageFunctionToolCallParam, ChatCompletionMessageCustomToolCallParam]:
+        from typing import cast
+        
+        tool_type = kwargs.get("type")
+        
+        if tool_type == "function":
+            return cast(ChatCompletionMessageFunctionToolCallParam, kwargs)
+        elif tool_type == "custom":
+            return cast(ChatCompletionMessageCustomToolCallParam, kwargs)
+        else:
+            # Default to function for backward compatibility (pre-1.99.2 behavior)
+            if "function" in kwargs and "type" not in kwargs:
+                kwargs["type"] = "function"
+                return cast(ChatCompletionMessageFunctionToolCallParam, kwargs)
+            
+            raise ValueError(f"Invalid tool call type: {tool_type}. Expected 'function' or 'custom'.")
+
+
+# Create an instance that can be called like a constructor
+ChatCompletionMessageToolCallParam = _ChatCompletionMessageToolCallParamConstructor()
+
+# Also create the type alias for static type checking
+ChatCompletionMessageToolCallParamType: TypeAlias = Union[
     ChatCompletionMessageFunctionToolCallParam, ChatCompletionMessageCustomToolCallParam
 ]