I think that would be more scrying than a spell per se. It would probably also depend on the spell you are trying to gain information on as well. For most spells though, either experiencing it yourself or casting it are the only ways to tell for sure what the effects of a spell are. In general many spells are specific as to what they do: cause nightmares or pain, heal, attract or repel certain things, etc. What the spell is for will generally tell you what it does. That said, the effects of a single spell will vary depending on the caster. Everyone's magic, and the way they cast it, is unique to them. It's the general that remains the same, not necessarily the specifics.