Advanced Class Guide has several teamwork feat that are meant to be taken by the character and his companion (eidolon, familiar, animal companion, etc.).
There’s a correct condition to only allow them on character with such companion, but there is no condition to allow them on the companion himself.
In my case, I needed to add the feat to an eidolon.
Affected teamwork feats:
Improved Spell Sharing
What is expected
To be able to take those feats on the companion.
Animal Soul, nothing in the feat description indicates the companion creature must have it (it's also designated as a General feat) - http://paizo.com/pathfinderRPG/prd/advancedClassGuide/feats.html
Improved Spell Sharing and Share Healing have been updated.