I will tell him/her/you
Le diré todo lo que quiera saber.
I'll tell you everything you want to know.
Debo hacer algo, ahora no le diré más.
I have to do something; I won’t tell him/her anything else now.
— Pinocho (2019)
Lo que le diré es sumamente confidencial.
What I'm about to tell you is highly confidential.
I'll tell you what you can do.