This tool is here to help you get access tokens for mastodon api clients. It's not for getting the client key and client secret, it's for turning those into an access token without you having to build out the whole flow just to dev with.
Yeah, this tool asks for your client key and secret. If you don't trust me, or want to run this yourself for some other reason, get the source from https://github.com/bkerley/mastodon-oauth-utility .
If you have any questions, hit me up at \@bonzoesc@m.bonzoesc.net