Symantec NetBackup™ 7.5 for VMware
|ArticleOC5162|||||Created: 2012-01-11|||||Updated: 2012-02-09|||||Article URL http://www.symantec.com/docs/DOC5162|
and thats all
The available command line tools expose pretty much all of the functionality that exists in the client. I don't think you should be looking for an API, rather use the existing utilities.
If you can elaborate on what you are trying to achieve more specifically, then maybe it's easier to help