Context dependent change of the tool tip?

It is really nice that shared commands can be disabled/enabled, as toolbar/menu items, based on the view.

However, how does one change the tool tip text based on the view. Say I have a screen1 and import operation has one meaning there, while screen two has different semanitcs for the same import action. While I can easily change the action instance I can not see a way to change the tool tip?

I tried to overwrite getFaceDescriptor () on my action command but it seems that produces no effect.

Anyone?

Thanks,
Alex