If you expect an OpenAI compatible API to use function calls, I don't think Ollama supports it yet (to be confirmed). However you can do it yourself using the appropriate tokens for the model. I know that Llama3, various Mistrals and Command-R support function calling out of the box.

Here are the tokens to achieve this in Mixtral 8x22 https://huggingface.co/mistralai/Mixtral-8x22B-Instruct-v0.1...

Pass function definitions in the system prompt.