I'm new in modding, I try to use Zerbu's Constructor to create a trait that can broadcaster some buff to another sim.

I try to add description in broadcaster: "Hmm... I think {1.SimFirstName} is good."

but I got "Hmm... I think _________ is good." in game.

{0.SimFirstName} is working, but {1.SimFirstName} was not.

Please help

I have a spurious feeling that {1.SimFirstName} just doesn't work in general, if I'm not mistaken - certainly not without some further snippet stuff that might be well beyond any modder's capacity.

It does work in the right circumstances, there's normally nothing complicated that needs to be done. In this case though I think the OP might need to do some workarounds.

Have you checked your participants in the buff or even broadcaster? It might need to be set to something else in order to work. Also, when you said "description in broadcaster" did you mean a notification or did you mean the buff's description? If you meant buff, then it's very possible that the game is just not capable of knowing that info without some workarounds, unfortunately. This is theoretical, but you could try adding an affordance to the broadcaster that is an immediate interaction where it saves the sim broadcasting as SavedActor1, then loot the buff to the people around them who are meant to receive it.