It depends on the context
If I'm just looking for a confirmation that my message was received, and the plans need to additional modification, a thumbs up is sufficient.
If I ask something like "Wanna meet up at the bar after work today?" And get a thumbs up, that's sufficient. We know where we're going and when, no more discussion really needed.
If I ask "you free to grab a beer this weekend?" and I get a thumbs up, that's bullshit. When are you free to grab said beer? Where are we going for it? We have details that need to be hammered out.