Criteria for 1st level of support

Hi there,

I am responsible of IT Help Desk 1st level of support. I am looking for
criteria which will help me to evaluate the agents by getting for example
good, very good and excellent or even satisfactory or need to improve.
1st level team are responsible to achieve the KPIs and solve the problem
online from 1st contact of the users.

So how to evaluate my agents!