It's a herbal 'supposedly' ayurvedic medicine made by a pretty big supplement manufacturer who also has a sideline in veterinary products.
Apparently there were human trials and they were inconclusive
This short term study does not suggest that Cystone® affects those
urinary chemistries commonly measured and known to influence calcium
oxalate stone formation, nor does decrease renal calcium stone burden
over a 1 year period. It is possible elements of the urine were
affected that are not typically measured (e.g., glycoprotein
inhibitors). A longer term study with more patients would be necessary
to detect changes in stone events or enhanced stone passage, or
effects on other stone types. In any new study of Cystone, the
botanical authenticity of each individual herb will need to be
documented by the manufacturer using high pressure liquid
chromatography. This short term trial failed to find evidence that
Cystone® prevents kidney stone formation and growth in recurrent
calcium oxalate stone formers.
Erickson SB, Vrtiska TJ, Lieske JC. Effect of Cystone® on Urinary Composition and Stone Formation Over a One Year Period. Phytomedicine : international journal of phytotherapy and phytopharmacology. 2011;18(10):863-867. doi:10.1016/j.phymed.2011.01.018.
I also found a list of the herbs it contains on Himalaya's website
Oddly some of these might have an effect on their own in studies -
this came up searching for Didymocarpus but this is in a test tube apparently.
I'd say it's inconclusive - and it feels a little like something that's given as a 'complimentary' medicine rather than something that's proven to work.