So this is my understanding of your requirement.
You want to know what fields are available for any given component. If so, the only place you can find that information is in your dialog.xml. However, it's not a straightforward process. The dialog.xml is defined in a specific way, so you have to search for all nodes with a sling:resourceType defined and retrieve those details. I don't believe there's a simple way to do that. You'll have to write some code to obtain those details.
Why because , if it is not your local , you cannot access /apps using a URL directly. If it is your local you can try something like
http://localhost:4502/apps/wknd/components/helloworld/cq:dialog.-1.json
However, if you're only interested in Content Fragment Fields, it's a different matter altogether. A Content Fragment is not a component, but rather an Asset that's available in your DAM (/content/dam).
For e.g if you have installed the WKND project , you can find the Content Fragment Model for author at http://localhost:4502/mnt/overlay/dam/cfm/models/editor/content/editor.html/conf/wknd-shared/settings/dam/cfm/models/author
This model defines the fields for each content fragment for Author.

To see the field details you can try http://localhost:4502/conf/wknd-shared/settings/dam/cfm/models/author/jcr:content/model/cq:dialog.-1.json

Hope this helps. Let me know if you are looking for something different.
Thanks
Veena ✌