Well, even if you were going to have the game create the objects automatically, you still have to determine what items you want the player to be able to create. Say for example you wanted to the player to be able to create an apple, you would use something like this:
create (apple)
And then once the apple is created, you would have to set all the different variables you'd need like the alias, description, etc.
Honestly, it's probably easier just to create the objects in advance unless there's some reason you have to do it this way.