REST API - How to get additional details

How to get additional details like: publish date, author, etc.? Date would be the most important. I need to get the list of most recent packages published in a repository (npm).

Not everything is automatically returned via the REST API. For example, creation date is covered in this unimplemented JIRA: https://issues.sonatype.org/browse/NEXUS-19055.
If you’re not seeing it likely it’s not implemented and probably either has or needs a ticket in our system for request.
Or in other words, we’re not hiding anything, what you see is what the API returns.
Hope that makes sense.
-Joe