This informal protocol declares a single method, view:stringForToolTip:point:userData:, which a class may implement to provide a tool-tip string to be displayed. For more information on tool tips, see the NSView and the NSView method addToolTip-Rect:owner:userData:.

@interface NSObject (NSToolTipOwner)
// Instance Methods
- (NSString *)view:(NSView *)view stringForToolTip:(NSToolTipTag)tag point:(NSPoint)point userData:(void *)data;
@end