-For portability, Arvados extensions should go into the @hints@ section of your CWL file, for example:
+For portability, most Arvados extensions should go into the @hints@ section of your CWL file. This makes it possible for your workflows to run other CWL runners that do not recognize Arvados hints. The difference between @hints@ and @requirements@ is that @hints@ are optional features that can be ignored by other runners and still produce the same output, whereas @requirements@ will fail the workflow if they cannot be fulfilled. For example, @arv:IntermediateOutput@ should go in @hints@ as it will have no effect on non-Arvados platforms, however if your workflow explicitly accesses the Arvados API and will fail without it, you should put @arv:APIRequirement@ in @requirements@.