Undo.

What it does:

1. Shows you exactly what it's about to undo, and asks first.
2. Takes back only what fieldtrip did: the tool it installed, the lines it wrote, the note it left.
3. Leaves anything you changed since alone, and tells you what it left.
4. Gives you the link to delete the key on the tool's website. That last step is yours.

It can do this because every fieldtrip add keeps a receipt of what it did. The receipt holds fingerprints of your keys, never the keys themselves.