- Add `type[]` for the `tool_cls` as it's expecting tool type class, not the instance (similar to #132420) - Add `set[str]` to `after` type as it's seems to be the way it's used the most widely, e.g. in "UI Tool Simple" example that comes with Blender: `bpy.utils.register_tool(MyTool, after={"builtin.scale_cage"}, separator=True, group=True)` Pull Request: https://projects.blender.org/blender/blender/pulls/133975