Hi,
The Google Analytics API only allow you to access keywords people used
to arrive at your website being tracked by Google Analytics. You
should definitely check the link Chris provided.
Also I would qualify your statement, "...shows the best suited 8
keywords." by asking best for whom? Google or your business?
You might find more valuable keywords for your business by looking at
which keywords convert well for your site, using Google Analytics and
our API.
-Nick