summonings determined by what ?

[avenged sevenfold]

in the majority of cases it is based on contract and in some cases things can be summoned by scrolls but yeah you cannot summon anything without the chakra need obviously

 

[Jin Hayami]

Signing the contract means you can summon them at any time. It does not however mean they will listen to you.

 

[fastrthnwind]

animal summonings: contract, blood, chakra,

inanimate summonings(weapons, objects, etc.):generic sealing scroll(depends on if retrieving from storage), chakra

the only exception to either of these summonings is FTG, which only requires chakra and a marker of some sort to summon a person from one place to said marker instantly.

 

[Klaves]

Animals require contracts, and they have to accept you as well. Weapons and other inn-animate objects just require the knowledge to seal them into scrolls like Tenten.