With Keyword Planner, we've combined the functionality of Keyword Tool and Traffic Estimator to make it easier to plan search campaigns. That's why Keyword Tool is no longer available. You can use Keyword Planner to find new keyword and ad group ideas, get performance estimates for them to find the bid and budget that are right for you, and then add them to your campaigns.
https://support.google.com/adwords/answer/3141229

Google Keyword Tool Has Officially Been Replaced By Keyword Planner

Google Keyword Tool Is Officially Dead, Keyword Planner Gets Lukewarm Welcome