Accuracy of Google Adwords Tool??

There is no definite way to tell if the Adwords tool is accurate because it includes data from all locations and all searches. For example, everywhere in the US, Canada and possibly globally. When you search, Google considers your location when showing both organic and sponsored results. So if you have a Dallas jobs site that posts jobs in Dallas, and you live in Dallas there is a good chance that when you search, your site will show up at the top, but if I search in Detroit, I wont see your Dallas jobs site anywhere, I will see Detroit job sites that may have some Dallas listings.

You can't count on your personal searches on Google to tell you where you rank. You may want to try some proxy searches or if you have a dedicated server, search from there or even set up an ec2 server for a few cents and search from there to get an idea of where you rank in other locations.

If you are using adwords for keyword research, you should use exact match and try to target geographical search results and devide that exact search count by 2, because on the google search engine near about 50% automated queries are fires. you will not get all those queries to your own website because other search results are also available on the search engine result page.