Well, for singling out which skills summon things, naturally ^^ Seriously though, the only proxy which gives any indication is the libram proxy, but that more by nature than design. Limited casting (daily limit) are not exclusive to summoning skills, such as item-granted skills like Give Your Opponent the Stinkeye. In fact, no combination of proxies can single out what would be a summon skill as there are some skills that can meet them and still not be summons. For example, Vent Rage Gland.
A clear definition could allow someone to iterate over them to aid in conjuring goodies and see which ones they have yet to cast or learn. Just as a simple example.