Is steam inventory helper legal?

chrome addons are legal, but i dont know if it would steal all your items, im more happy to use Enchanted Steam that provides near same stuff + more

No it isn't, and the police have been alerted to your location for merely asking.

i`m using that for more than 3 months ... so no ...

So far no. It helps a lot in my card trading too. Makes value checking of items very convenient.

Okay thanks.