Azure API management cache size

Azure API management has different size caches depending on the pricing tier, and has the ability to add an external Redis cache to extend the default cache size. Is there a good way to determine when the cache size would benefit from being increased? For example, is there a way to see how much data is being cached at any one time, or how often calls are hitting or missing the cache? The only thing I've found so far is indirect, by measuring the average response time and average service response time under the Analytics->Operations.