For APIs, would be nice to add sections with headings to the intro description, and those headings are added to the table of contents. ReDoc does this, see example: ReDoc Interactive Demo
Not sure if this is actually in the OpenAPI spec though, but thought to share.
I believe that the font size as is is clearer as this shows that it belongs under the API title, not a main section. Please feel free to modify using Custom CSS to modify style as needed.
I feel that this might overdo it for most of the API references we host as they have only one server URL. I do not believe it is standard to have a separate section for it. I’ll keep this tasked until we get more momentum on it from other users.