Using jQuery Tools with Drupal 7
You're approaching this correctly in trying to add this in your own info file - not every jQuery library needs its own Drupal module and its often more overhead than its worth to try and set one up. If the jQuery tools module is what you need but its not compatible with the current version of Drupal 7, than use jQuery Update module to upgrade your version of jQuery.  

If all you need is the overlay and you're not tied to the jQuery Tools implementation, you have a couple of customized Drupal options that should be easy to implement:


The built-in overlay functionality in Drupal 7.x core (see https://drupal.org/node/1087026 for guidance on how to implement)
Use one of the specialized overlay libraries - best one I've found is Colorbox, which has a Drupal module with easy to implement solutions (i.e. no hand-coding javascript)