Step of api first methodology: a tag system

I refer to . The idea is, after wrote the stories needed to define interaction, and thus functions, of the system we are going to implement, the next step is to define an api, then proceed with API definition, then implement backend, frontend, and cycle this way redefining stories (or adding), refining api, change frontend and backend. This is not water fall, is just a sequence to follow in the cycle, something like rithm keeper (metronome?), of development process.

Well, now I am interested in backend organization of API. I fail on looking for a graph library which could produce something of mean for me. The problem is how to group API calls, I assume that is good to categorize those by field of influence, but, of course, there are intersections between these fields, just an example

call, description and tags
AddUser add a user user
GroupAddUser add a user in a group group, user
RequestGroupAddUser add a request to add a user to the group request, group, user

Hand wrote dashboard works, but what about a tool to visualize this?

Here look clear that add user go to user set, but depending of the actor using the system things could become unclear, as it is on most API available, it assumes some point of view. This point of view should be explicit, something like “this part of API assume the view of system administrator”, thus grouping request in a request api bundle because it is important to have getPendingRequests and addRequest.

A better tool than spreadsheet is needed, or maybe a more effective way to use it.