Metavariables have problems with garbage collection and intermediate results. Mapping of variables to URL should be generic. A URL is for returning information to humans and is not good for computers. Consider the size of the returned information. Return a small amount in a variable and a large amount by some other means.
Data remains available until next run.
A URL implies HTTP, that is, not UDP only. Yes, to say results are available. Intermediate results can go by push. Final results can go by pull that causes script to run. A script can push as it wishes.