I am looking a way how we can add description of fields to the views. In BQ UI there is no way to add description, its only for tables.
Is there way to do it programmatically using api's.
It is not possible for views to have field descriptions at present. There's an open feature request on our public issue tracker to implement this. You can star the issue to let us know it's something you're interested in and we'll prioritize accordingly.