Since i mentioned the universe of summons, and creatures of summon, i should dulge into that. Summons are as you think and know, beings that are capable of summoned through the use of being a summoner brew, or some other method. Summons tend to vary in size, design, features, mentality, and most importantly, the utility of them. Some are made for battle, other for friendly chores, or to assist the user in another way. Even with that said, depending on the summoner they can be used for all sorts of things such as prescribed, even if they are not.
Some summons are known to being actually be summon in oppose to being ever present by the summoner in question, some to have a mind of their own along with a personality while others are drones idling about without thought or going by their primal extinct. The user, however, has complete command over the summons and said summons must obey; there is little exceptions of it, the summons in question cannot even kill the person unless given a circumstance involving an order.
There are many different types of summons from one that are by themselves to others that tend to work better as a group based on personal affairs.
The one thing that can be done with a said contract with a summon is that one can improve upon the being. This is done making specific deals such as sacrificing or giving some sort of energy in return. Otherwise, summons tend to improve on their own.