Visualising Complex APIs Using API Map
medium.com
medium.com
In fact, if your audience is familiar with these sorts of diagrams, I wonder if it'd be more readily scannable if you denoted the cardinality of the relationships with the sort of notation you'd see in ERDs or CDs? (Personally, I'm a big fan of Crow's Foot.)
I think I didn't see one since like ten years?
(1) - That detail is covered by API specs like Swagger (2) - Two endpoints that return the same resource (of the back of two different operations on the same resource) may return a slightly different format/field. This is up to the developer of the API and best captured in API spces.
(For that matter, if you output the diagram in a format that supports hyperlinks like SVG or PDF, you could link from the diagram directly into Swagger.)
You brought another very good point about being able to hyperlink directly into Swagger, something we have been talking about a lot recently. Unfortunately, we have not come across a tool that does this satisfactorily.