1) Thanks for posting your full version with build. Many new users skip this and it's very cool you did not!
2) Please try to add your installation method as well (full version, something like Vicibox 8.X.X?)
3) You did not supply a lot of information, so I will extrapolate my guess of what's going on, and answer your question along the way.
4) Direct answer: The non-agent api "add-lead" method does not have an option to only add a lead if the lead has a specific disposition. You would need to modify the code or create a new php file to filter your requests to make that happen.
5) Shall I assume that you are using a Vicidial server to add leads to a different vicidial server (owned by someone else?) at the disposition moment based on the value of the disposition for future calls? If so, your best bet is to create a php file that checks the disposition and then passes to the non-agent api only if it matches. A really good script for this would allow the "match-list" to also be in the url as well as the "bounce to" url, so it would be usable for pretty much any future similar need.
6) If that's not the case, if you are in fact creating a new lead on the same server ... I am shaking my head sadly that you would do such a thing. I bet there's a better way to do whatever it is you are trying to do. I've never seen a good reason to have the same lead twice on the same vicidial system. Always open to the unique situation that may require it, just haven't heard one yet. lol