Wishful thinking. The AdWords API is a low level way to access Google's system. You can create a new ad word campaign and add keywords to it, but Google doesn't have anything to scrape keywords off of a website. What you describe is a high-level functionality that I doubt they would ever consider adding because what counts as a "keyword" is entirely too dependent on the function of the website. That said, it wouldn't be hard to implement what you described using Perl LWP to scrape your website for keywords and the SOAP::Lite interface to AdWords.