The authors of the tool created something that can be used for copyright infringement.

The tool itself lacks agency, it did what it was programmed to do.

If you took the tool's suggestions and proceeded to published a derivative work, you may have infringed.

This really doesn't feel any different from P2P filesharing services. Rightsholders have targeted tool publishers in the past, because they are the largest single target and not anonymous; but ultimately the infringement is performed by the end user.

This isn't complicated at all. You copied the code, which isn't an issue until you then go on to do something which infringes the license (e.g. publish under a different license, publish binaries without publishing source, publish without attribution, whatever it is that the license requires).