action=setnotificationtimestamp API is not documented anywhere.

The documentation should be created as API:SetNotificationTimestamp  page on MediaWiki.org, using a structure similar to other API documentation pages (list here).

Automatically generated documentation can be viewed at https://www.mediawiki.org/w/api.php?action=help&modules=setnotificationtimestamp, your work should expand on it.

In addition, the docs (both on mw.org and in code) should mention something about
marking pages/revisions as visited, since that's how it's called in the UI
("notification timestamp" is an internal term).

See this bug report for more information. Students are required to read Wikimedia's general instructions first.