will inform, will notify, will warn
Se por acaso ele vier aqui, eu te avisarei imediatamente.
If he happens to come here, I’ll let you know immediately.
Avisarei Sternberg que terei companhia.
I’ll let Sternberg know that I’ll have company.
— Morangos Silvestres (1957)
Eu te avisarei quando estiver terminado.
I’ll let you know when it’s finished.