The amulet is in tune with Jim’s emotions. That’s how it deactivates after a fight’s done, because it senses he’s no longer in distress. Blinky says the amulet requires the incantation to activate, but we witness once in the beginning, before Jim’s begun to master the amulet, it activating out of the blue at school without him ever speaking the incantation. That’s how he ends up at Romeo and Juliet tryouts wearing the armor of Daylight.
We also witness Jim will the amulet to him in Claire and Present Danger. The amulet doesn’t activate per se, but Jim (literally) calls to it and it responds, rocketing to where he is because Jim needs it.
It makes me wonder like, can the amulet also activate based off of Jim’s emotions? Will Jim always have to speak the incantation to activate it, or will there come a point in the future where Jim and the amulet are so in synch the amulet will just know when Jim needs it to activate without him having to say anything? Just based off of his emotions or what he wants to happen in that moment.