Your idea probably isn’t unique.
But then again you probably haven’t found anybody that has done it the way you plan to do it.
So don’t spend your time asking people to sign NDA’s or telling them half of the story.
Just go execute on it.
If you not sure, or need help, then talk to people.
If your talking to them because your not sure, tell them the whole thing so they can give you honest feedback.
If your talking to them for help, tell them the whole thing so they can help in the best way they know how.
If somehow they “steal” your idea and execute it faster, better or bigger than you.
Then for your next idea just execute, don’t talk.
(and maybe have a look at how they executed your last idea and reuse the bits that you think worked)
Ideas are easy, execution is hard.