Clicking on any item displayed on the API doc (http://localhost:8080/nuxeo/api/v1/doc) to unfold them doesn't do anything when Drive is not installed on the server. The following error message is displayed when we arrive on the page:
Unable to read api 'drive' from path http://localhost:8080/nuxeo/site/api/v1/doc/drive.json (server returned undefined)
This makes the API doc unusable.
Installing Drive fixes the problem.