tú cuéntaselo

tell it to him, tell it to her, tell it to them, tell it to you (formal)

→ contar
cuént to count + a informal singular command + se Indirect object pronoun (to him/her/them/you) + lo Third-person singular direct object
verb · 2nd-person singular informal Rare #47,976
tell it to him, tell it to her, tell it to them, tell it to you (formal) The pronouns attached to the verb mean “it” and “to him/her/them” or “to you” (formal), depending on context.
SP: Cuéntaselo a Ana cuando llegue.
EN: Tell it to Ana when she arrives.
Conjugation of contar

Llama a Montes y cuéntaselo.

Call Montes and tell him about it.

— El guardián invisible (2017)

Vale, pero cuéntaselo.

Okay, but tell them about it.

— 7 años (2016)

Cuéntaselo todo, hazlo.

Tell them everything. Go ahead.

— Hogar (2020)

Cuéntaselo, no pasa nada.

Tell him about it; it’s okay.

— 7 años (2016)

Cuéntaselo, que se va a alegrar.

Tell him, he’ll be happy.

— Jaula (2022)