I like to claim that dinosaurs used tools, because some of them swallowed gastroliths. No reason a tool can't be internal.
Oh wait, the article says external is in the "scientific definition". Fine.
I swallowed a rock when I was a kid (ok, maybe calling it a "rock" is being a bit dramatic, more like a pebble), does that make me a tool?
....wait, no
I swallowed a rock when I was a kid (ok, maybe calling it a "rock" is being a bit dramatic, more like a pebble), does that make me a tool?
....wait, no