We've been working with GetCategoryFeatures to help alleviate certain data validation problems (e.g. certain categories only support certain product conditions, etc.). We're curious how/if others are interacting with this. I.e. are you calling GetCategoryFeatures dynamically, as-needed, or are you building a cache of all the eBay categories and their unique properties? It appears, at least from the documentation, that child categories can differ from their parent categories, so it appears that this needs to be invoked or cached for all categories, and not just top-level categories. Thanks in advance for any tips.