Abilities » Tool Concealment
If Banette's "Tool Concealment" ability is active, can I attach multiple Tool cards to my Pokemon?
No, you cannot.
Source: Roaring Skies FAQ (2015-05-07), TPCi Rules Team (2015-05-07)
Abilities » Tool Concealment
Banette's "Tool Concealment" ability means Pokemon Tool cards simply have no effect. They are still considered as Items and Pokemon Tool cards, so "Garbotoxin" still works, "Startling Megaphone" would be able to remove them, etc.
Source: Roaring Skies FAQ (2015-05-07), TPCi Rules Team (2015-05-07)