D&D 5E Detecting concentration?

[Theo R Cwithin]

Is there a RAW way to tell if a caster is concentrating on a spell?

I've just assumed an Insight or Arcana check or something, but can't find a specific rule for it.

A few situations to illustrate:
PCs try to discern if a sketchy NPC is concentrating on a charm or scry or something during a negotiation.
PCs want to determine which enemy caster to target in order to drop an ongoing debuff affecting them.

 

[DND_Reborn]

There isn't a rule, per se, that I know of.

Making a check seems reasonable, and we would probably do it the same way.

I would, however, make it that if the checker can cast the same type of magic have it with advantage, or make it harder and say if they can't cast the same type (divine, arcane, primal) it is with disadvantage.

Just depends on how complex you want to make it.

 

[Horwath]

Concentration is already too easy to break, so I would rule that are no visible effects on the caster.

Unless you see direct effect of the spell and you character knows that that spell requires concentration.

 

[Cap'n Kobold]

I'd probably allow an insight check to determine if someone is distracted by something. However detecting actual concentration wouldn't generally be possible.

 

[bedir than]

Since there are zero concentration spells that don't have game effects, I would say the rule is the Xanathar's Guide recognize magic rules using Arcana.

 

[R_J_K75]

Just look for the person who looks like they're pinching a loaf or trying to hold one back.

 

[Theo R Cwithin]

Since there are zero concentration spells that don't have game effects, I would say the rule is the Xanathar's Guide recognize magic rules using Arcana.

Ah, okay! I'm not very familiar with XGtE (It's on my to-buy list.), so I wasn't aware of a rule like that. I'll check it out.
Thanks for the tip!

 

[ad_hoc]

I like ruling on the cinematic side of things so I think there should be some obvious effect that a caster is maintaining some sort of magical thing.

That said, something more subtle like a charm that was cast before the PCs showed up might be different. I would probably check against their passive Insight in that case. If they were spending the scene studying the caster in question then they would probably be rolling a Wisdom (Insight) check.

 

[bedir than]

Ah, okay! I'm not very familiar with XGtE (It's on my to-buy list.), so I wasn't aware of a rule like that. I'll check it out.
Thanks for the tip!

Quick version - reaction if you watch being cast, action to identify effect after casting. DC is 15+spell level. Advantage if you have a class able to cast the spell.

 

[Horwath]

Ah, okay! I'm not very familiar with XGtE (It's on my to-buy list.), so I wasn't aware of a rule like that. I'll check it out.
Thanks for the tip!

By XGtE you MUST observe the casting components of the spell while it is being casted(V,S,M) or spell has visible effects. It says that it is impossible to determine the caster of a spell that is in effect.