Hi
an agent is selected from a CSQ ( Contact Service Queue ),
now agent selection can be based on Resource group or Skill based.
Call entering into UCCX are answered on FIFO basis, but agent selection is not like this.
When you assign diffrernt skills , you have to set a selection criteria among all those skills that who will be selected first,
for eg . agent with high competence or agent with less comptence value.
if there are 2 agents with same skill, same competence value , usually longest idle agent is selected for the call.
so it totally depends on your config ,
if you can share screenshot of some CSQ , then i can answer based on that config , which will clear more doubts that you have.
Regards
Anurag