Can GitLab's rendered openapi.yaml make API calls?

I’ve searched everywhere but I haven’t found a clear answer whether or not GitLab’s rendering of the openapi.yaml project file is meant only for viewing purposes or if it actually can be used to test the endpoints. I tried to test the endpoints through the rendered file but got:

Failed to fetch.
Possible Reasons:

Network Failure
URL scheme must be "http" or "https" for CORS request.

This page states that the OpenAPI viewer renders the content, but doesn’t mention the ability to make API calls. I just want to make sure it isn’t able to do that before moving on.