D&D 5E question on lower level spells in higher level slots

[TaranTheWanderer]

Similar to another thread about dispel magic- Would you rule that the viewer knows that the magic missile is being upcast to know that he needs an upcasted dispel?

As for the OP, I always thought it would become a 7th level spell instead of using a 7th level slot.

Probably only if they had detect magic up and could see the amount of power being gathered. But then I might just tell them it’s being upcast and let them decide the slot. I’m not really sure since I’ve never had to adjudicate that scenario.

 

[Blue]

Pretty easy. You'd see the number of darts

That doesn't work. Counterspell has to be while the foe is casting the spell. It's not until the casting is complete do the effects of the spell occur. So by the time you can count the missilkes it's too late, the casting is omplete. Xanathar's goes into the difference from telling what a spell is from it's effects (after casting) and from the casting itself.

 

[bedir than]

Xanathar's goes into the difference from telling what a spell is from it's effects (after casting) and from the casting itself.

I'll re-read.

I would consider the effect of magic missile to be the damage done, not the flashy lights.