Don't "boil the ocean." You will quickly find that in order to gather data and get maximum value from your service catalog that you will also need an application catalog. And a data catalog. And an organization catalog. And a capability catalog. And a technology catalog. I think you see my point. Are there tools that can do all of this? Absolutely! Just look into enterprise architecture repository tools.
When you gather data for the first time, it can be an enormous effort that can quickly become a time sink with little return if you don't take it one step at a time. While I suggest focusing on the consumer first, you do have to prioritize your needs and pick the one that will have the most impact on your organization.