On most nonbook items, patrons can't just read the summary on the dust jacket or skim the table of contents. An item's contents can usually be summarized in two to three sentences. Remember that you are not trying to sell something, you are letting the patron know if the item will meet his or her needs. Contents notes can also be invaluable, especially for sound recordings. If a teacher needs a particular piece of music, but the only information you have in your catalog is the title of the collection it's on, he or she will never find it.
Some videos also contain multiple programs, or have segment titles that are very descriptive.
With so many people wanting to search by keyword, adding summary and contents notes can be well worth your time. There are many other prescribed notes for nonbook materials. Decide which notes are really important for your catalog, collection, and patrons, and leave the rest out. Do be cautious about omitting anything considered mandatory. You may migrate to a new automated system or share your records some day, and will want your database to be up to standards.