Hi.
I occasionally get asked about what a reasonable rate for querying the API of a Wikimedia wiki is for a particular script or tool. I don't really know the answer other than "be reasonable" and "specify an informative User-Agent." That's essentially what I said when asked here: https://meta.wikimedia.org/w/index.php?title=Tech&diff=3569658&oldid...
If there's an authoritative answer (on Meta-Wiki or mediawiki.org or even wikitech), that'd obviously be ideal. I'd also settle for a mailing list post. I looked at https://www.mediawiki.org/wiki/API:Main_page to see if it mentioned "limit" or "rate", but nothing came up. It's a fairly common question; it should probably be a bit easier to find.
MZMcBride