I actively use "metrics" request to the RESTBase API in the Wikimedia project.
But there is no description of this functionality on the documentation page:
https://www.mediawiki.org/api/rest_v1/?doc
If this is a standard feature, it should be described. If not, please let us know about its prospects.
@Krassotkin The list of available API endpoints is different on different domain, so you need to look for the documentation on the same domain you use to call the API. More concretely, here's the docs for the metrics endpoints: https://wikimedia.org/api/rest_v1/?doc=#!/Pageviews_data/get_metrics_pageviews_per_article_project_access_agent_article_granularity_start_end