Just for clarification, I'm wondering which action happens first? Would you check your opponents dial with Agent or would you decloak first?

Thanks in advance.

Intelligence Agent happens first. Decloak happens after all other abilities of which Intelligence Agent is one.

At the start of the Activation phase, after players have resolved all other abilities that trigger at the start of the Activation phase, each ship may spend a cloak token to deCloak

See the current FAQ for the full text of the revised decloak rules.

Intelligence Agent happens before decloak.