I own a website and I'd like to be able to have an history of how some page and keywords ranked in google over time, to be able to understand if certain changes I made have positive or negative effect.
Now, I think that doing it by hand is a bit error prone and time consuming and I'd like to understand if I can write a simple tool to do that.
Unfortunately, from what I can read from the Google TOS (Term of services) is not allowed to crawl their result, instead they suggest to use the Google Custom search API.
And here is the question. As the custom search API
are unlikely to match those returned by Google Web Search
how can I acquire accurate informations about keyword positioning without violating the google TOS?