You're close. Perception allows you to notice things that can be seen or heard (or in rare situations smelled, or whatever). Investigation allows you to deduce, uncover, or otherwise find hidden things. So if you spot (with perception) a tripwire (or something), you can disarm it (with thieves tools). The new tool rules in Xanathar's suggest that if you use your thieves tools while rolling Investigation to search for traps, you can roll with advantage. The idea here is that the tools help you to poke and prod at things carefully (because the results of failing the Investigation to search for traps is usually that you set off the trap.)
On, in other words, the short answer is "depends on the trap".