When you select a part from the parts palette, its default name is displayed on the status line at the bottom of the Composition Editor, and in the hover help window for the part. The default name is based on the part's class name. You can change this default by adding a displayName class method to your part's class. Here's an example you can use for the timer part:

To test your changes, select your part in the parts palette. From the Options menu, select Modify Palette > Delete Part. Now, in the System Transcript window type MyTimer addPartsToCatalog, select the text and then Execute.

You should see the new descriptive name in the status area whenever you select the part. You should also see the descriptive name in the part's hover help window.