A colleague of yours who supervises a similar department in another local institution telephones you and asks for your assessment of a former employee of yours who is applying at his institution. Should you continue the call? Why?

How much information to provide

A colleague of yours who supervises a similar department in another local institution telephones you and asks for your assessment of a former employee of yours who is applying at his institution. Should you continue the call? Why? How much and what kinds of information should you provide? Why?