Something defensive to give thieves a little bump. Thinking would work essentially like wilderness familiarity but in civilized settings.

My thoughts on thieves are how they are evasive and tough to hit in an urban setting. Would be useless when they're out of their element and i think it would be a huge benefit to all thief paths.

This already exists, and your name is already almost it.

See https://www.carrionfields.net/helpsearch.php?keywords=urban+agility