Recently I was discussing spells with someone, and if they should be well defined or loosely defined. Interestingly, we both argue our positions based on what will encourage creativity the most. UbAh advocates loosely defined spells so that players can add on their own spins to solve problems outside of combat. I advocate strong definitions so that players can do the same. I think UbAh’s argument, that if you can think up creative things to do with magic, and then can do it, it encourages creativity, is pretty obvious, so I’m going to spend some time stating my own, less obvious argument.
I think challenges and speedbumps are important. The fun in roleplaying games comes from challenges you have to overcome; a game where you walk into the dungeon, find no traps and no monsters is pretty boring, as my players can tell you when I tried to run the sample adventure included in the 2nd edition Traveller book on the fly. Heck, it doesn’t even make a good story. You need challenges to make a good story, a good game and so on.
Think about this: If the players have magic that can do anything they can think of, why don’t they just use magic to bypass your puzzle? I’ll give you an example from one of my favourite Living Greyhawk Ket adventures: There is a monk tied to a chair. The chair is on a platform that is suspended 30 feet or so over a deep pool of water. It is suspended by a long, greased, pole. The monk is able to keep balanced on the platform, but she has been doing it for a while and is getting tired. You need to rescue her.
Now, if you have a spell that can undo her ropes, or levitate her and her chair over to you, the puzzle is trivial, no creativity is needed; you need to unscrew a screw, and are holding a screwdriver. However, if you have magic, but NOT one of those effects, things get more interesting. For example, one solution I’ve thought of is to use reduce person on a gnome or a halfling to make them tiny and just really light, tie their feet to the middle of a rope, then have one PC on each side suspend them where he or she can untie the ropes. Another is to use stoneshape to bend the rock around the pole, so it can no longer rotate freely, things like that. You don’t have the exact spell you want, so you have to use what you are given.
Now, this depends on your spells working the same way each time, or else you can’t be sure if your solution will work in any specific instance. You need enough flexibility in it to allow any pretty much any spell to be used outside of combat, but if you have too much freedom the players can do exactly what they want, which removes the need for them to be creative.