General GUI Development: Acceptable tooltip string length?

Question

I'm putting the finishing touches on a GUIDE (MATLAB) developed GUI. I wanted to add tooltip strings to help the user but I don't want to overwhelm the user. Here are some examples of tootip strings that I have so far:

These are tooltip strings for 4 radio buttons that I have in a radio-group panel.

Apply annotation to highlighted region of the selected electrode pair

Apply annotation to entire data range of selected electrode pair

Apply annotation to entire data-set of selected lead (6 electrode pairs)

Apply annotation to entire data-set for both leads (12 electrode pairs)

This is the tooltip string for a toolbar push button

Press to start annotating. Depending on selected mode, a highlight tool or window will appear

Are these too long or are they an acceptable length? Currently they convey all the information that I need to convey to the user. If these are too long, what could I do to shorten them?

Bonus question: Is there a general short-hand that is used for these types of user "hints" or "tips"?

Answer 1

As far as length goes, they should be as short as possible and they should be understandable by whatever your user base is. So the length also depends on your user base because you may need to add more or less of an explanation depending on your users.

Also, as DA01 said, you should make sure that your UI actually needs them, rather than needlessly cluttering your interface with them. Sometimes users will rest their mouse on a part of the screen to think, and that could activate tooltips and bother them. So only use them when necessary.