ok a bit of a practical question now. I have a tool which I need the assistant to invoke when the call starts. this means in the system prompt I should just say :

caller_number : {{from}}

or

caller_number : {{call.customer.number}}

what I need is to have the caller's number available / exposed to the system prompt so it can call a function from the tools to get context about the caller. cc @Kings_big💫 @Dang Hai