How to prompt a model to use a specific language for the function call?

We are using function calling to extract some data from text in a structured way. Most of the time, the text provided in the arguments of the function call is in the same language as the input text and the set of prompts and descriptions for function call parameters.

However, there are cases where the model decides to respond in English. This is suboptimal for our use case. Is there any way we can improve stability here?

Thank you.

Did you put it in the Assistant prompt? Like 'when calling function xx make sure that all arguments passed are written in language x. Never pass English language sentences to the function"

No, I haven’t tried it that way. Thank you!