I have a Google API key and I joined the Keyword tracker. My question is, how many keywords can I check per day within the first 100 results, without being punished by Google?
You won't be "punished" by Google, you just won't be able to make anymore queries using your API once it has been used until the next day. I have hundreds if not more of keywords and have never had a problem. I'm sure others have even more. I only run the search once a day so I have never had an issue with it. It allows 1,000 queries a day so I believe that would be 1,000 keywords if you only used it once a day although I'm not sure exactly what counts as a query in the process