I discovered that api 2.9 has already been released and that the current api is actually well past 2.9 - It's a little confusing trying to navigate the api versions in the documentation.
I see that in the latest API the description for workbooks is available using fields.
I have not found anything regarding hit counts for workbooks however.
Workbook description isn’t available in versions prior to 2018.1. For more information on using fields (“description”) in the RestAPI v2018.1 and beyond please see here.
“The <usage> element is included in the response only if the method has includeUsageStatistics=true in the URI.”