Tools inserted in the message as JSON instead of directly called

[Simone2498]

Hello everyone,
I'm testing Ultravox and it seems to work very well, if not for a problem with the tools. I connected it with Twilio and I have a function to close the call. I created a temporaryTool and everything seems properly set, I don't get any error, and using the endpoint calls/{id}/tools I can see it is properly loaded. However, instead of calling the tool, the model appends to the last message the JSON of the function and reads it loud. I don't understand where is the problem, but it seems that the prompt has no effect.
Can someone help me?
Thank you
Simone