Look at it this way. If I'm at a REPL, and I have this:

    o = SomeObjectOfUnknownCapabilities.instance

then I can do this:

    p o.methods

...and see what I can call. The method names give me no guarantee as to what the methods will actually do ("slice" could return a subset of data, or cut a pie), but once I have the verbs, in either case, I can experiment. That's the important bit here—discoverability isn't about knowing what new things do right off the bat, because that's impossible unless there's a finite set of things you can do; discoverability is simply about being told the affordances, so you can manipulate them and observe the results.