It should work with API keys, if not, send us a bug report. Sorry about that, the initial wording of that line (middle bullet point) in announcement was confusing. I’ve updated it.
Apologies for the miscommunication, we intended to say that you can call into your own tooling and then have that tooling call this API. I understand the original wording was confusing, it’s been modified.
For what it’s worth, we are actually currently looking into making it possible to call some of our web APIs like this from in-experience!