NOTE: The concurrent use of Chat Functions and Azure Chat Extensions on a single request is not yet supported. Supplying both will result in the Chat Functions information being ignored and the operation behaving as if only the Azure Chat Extensions were provided. To address this limitation, consider separating the evaluation of Chat Functions and Azure Chat Extensions across multiple requests in your solution design.
From https://learn.microsoft.com/en-us/dotnet/api/overview/azure/ai.openai-readme?view=azure-dotnet-preview Assuming it's similar in the JavaScript SDK, although I'm not sure why it's the other way around for you.