The DeltaCloud class currently has a method #deleteKey. The Deltacloud server reports available actions on objects and does so with Keys. This approach is perfect REST style as it offers links to available actions.
Keys currently have a destroy action and deltacloud tools do unmarshall this correctly. The tools implementation should therefore remove #deleteKey from the DeltaCloud class and offer such a method on the key that then delegates to the appropriate (destroy-) action.
The current tools implementation already offers this approach for instances but took a shortcut with Keys to have higher prio items for CR1 implemented.