Ask HN: How should we handle calls from other vendors?

We are a startup that provides Business Intelligence services to car dealerships. We have been approached several times recently by other software vendors -potentially future competitors- that want to know more about our technology. We are wondering how should we approach these kind of calls? Should we ignore them with the fear of revealing too much info? Should we be open about it and tell them how are product works? We have been quite open until now. If you have been in a similar situation what was your experience? Thanks!