diff --git a/specification/cognitiveservices/OpenAI.Inference/models/completions/tools.tsp b/specification/cognitiveservices/OpenAI.Inference/models/completions/tools.tsp
index d947beae32fe..a7d973b15052 100644
--- a/specification/cognitiveservices/OpenAI.Inference/models/completions/tools.tsp
+++ b/specification/cognitiveservices/OpenAI.Inference/models/completions/tools.tsp
@@ -40,6 +40,13 @@ model ChatCompletionsNamedFunctionToolSelection
   @doc("The object type, which is always 'function'.")
   type: "function";
 
+  @doc("The function that should be called.")
+  function: ChatCompletionsFunctionToolSelection;
+}
+
+@added(ServiceApiVersions.v2023_12_01_Preview)
+@doc("A tool selection of a specific, named function tool that will limit chat completions to using the named function.")
+model ChatCompletionsFunctionToolSelection {
   @doc("The name of the function that should be called.")
   name: string;
 }