It’s actually quite common to use Swagger JSON v2 declarations to import REST services and start interacting with them.
Unfortunately for WebSphere Commerce is not so easy.
to download JSON declarations for every service one by one (not so friendly).
A quick tip about Swagger UI: if you want to get Search API declarations instead of Commerce runtime API, please change the base URL to http://localhost/search/resources/api and press Explore
If you’re just specifying Swagger UI URL and hit Enter, a https redirection will be forced and Swagger UI cannot be accessed with recent Chrome or Firefox versions because of a missing CORS configuration on WebSphere Commerce (CORS issues will be solved soon with JR55289 fix, a back port for v7 of v8 CORS mentioned by Bob Balfe in his post)
Then I had to open a PMR (25672,756,000: thank you Steve Boggs) and ask to the support for the procedure to create a Swagger file and upgrade it to v2. After some back and forth where our Commerce Technology Advocate helped too, we finally generated a valid v2 Swagger JSON file for runtime and search server
You just have load it on your preferred tool and start testing WebSphere Commerce REST interface