I think that's a very forward way to go about it, but I'm pretty sure authors would like that, because it means they created something you liked enough to use yourself.

I'm not sure it's so much about whether I've been copied myself, I just wanted to make sure that I didn't offend an author I liked very much. I ended up asking her (because I remembered where I got the idea from, which of course is very handy) and got permission as well.

As you said, I think it would be nice as an author to be asked, simply because it's sort of like the other author is taking part in one's own creative process.