What is the best evaluating tool you use to measure your team performance ?

Measuring team performance is relatively easy.  Did the team achieve its goals without causing unexpected difficulty elsewhere?  Since you already know what the goals are, and goals worthy of the name include a measurement system, answering the question is easy.

Measuring the performance of individual team members is difficult in general.  I have found the best way is to ask myself, "In the end of the day, is person X any good at their job?  Yes or No" and force myself to answer.  Once you know the answer (Yes or No), and only once you know the answer, you can add modifiers.

I think easiest way is always the best way......  So team performance’s KPI can be used effectively.

KPIs measuring team performance would most likely be qualitative in nature. But a process or quantitative metric could also be used to evaluate teams but depending on the nature of the project, product, service or industry …… since team and individual activities may involve the utilization of specific processes or quantifiable activities to accomplish goals.