All right, so you understand that you can't look for F&O entities in BC documentation.
While the linked documentation gives you some details, it's not actually that informative. Yes, there is a page about each operation of each entity, but it's almost the same in all cases, because the structure is defined by OData and the only thing that differs is the name of the entity. The documentation is (I believe) generated from Open API specification.
One useful thing there is an example of data (e.g. in Create purchaseOrders), nevertheless if you have an existing record, you can export it to get an example.
Would it be possible to generate such documentation? Yes. The list of entities, labels, fields etc. can be easily obtained from metadata. It would just need some solution for the sample data. Is there any such documentation already generated? No, at least I'm not aware of it.
I'm a big fan of Open API specification and I would love if it was available for all web services exposed from F&O - it gives you documentation, but it has several more benefits. It's not that useful for CRUD operations on entities, because they're all the same, but it would help a lot with custom services and OData actions. I discussed this topic in Open API for JSON-based custom services in AX 7. Sadly, no such a thing is available.
If you tell us what kind of information you're looking at, we might be able to tell you how to get it (or that it isn't available at all).
