Function Calling not following format given to the assistant

I have a use case where I am using function calling to determine which API to data from and returning that data to the bot to get response.

The response needs to formatted in the a certain way and I have mentioned that in Assistant Instruction while defining the assistant

When function calling is not used the response is formatted as specified.

But when the function call is used, the bot response seems to completely oblivious to the instructions mentioned in the assistant descriptions.

Has anybody experienced this? is there a work around?

Random suggestion:
Does putting the formatting instructions into the function work?