diff --git a/libs/langchain/langchain/chat_models/openai.py b/libs/langchain/langchain/chat_models/openai.py
index cf0bfe3f9389f..5d1a8eaa1fd92 100644
--- a/libs/langchain/langchain/chat_models/openai.py
+++ b/libs/langchain/langchain/chat_models/openai.py
@@ -697,7 +697,7 @@ def bind_tools(
         """
         from langchain.chains.openai_functions.base import convert_to_openai_function
 
-        formatted_tools = [
+        formatted_tools: Dict[str, Union[str, dict]] = [
             {"type": "function", "function": convert_to_openai_function(tool)}
             for tool in tools
         ]