I've got a website with thousands of pages. I feel like the munchkin code isn't on every page - but the ones I've spot checked, it is there. Is there a tool that will check a full site map and verify the pages are tagged?
As long as you're not including Munchkin via something overly complex like GTM, then Munchkin.init should be in the page body. Send me the sitemap and I'll check all those pages (my personal answer is the command line tool cURL).
We use the Screaming Frog site crawler to look for the Google Tag Manager script (and thus the munckin) on every page.
They have a free trial that lets you crawl up to 500 pages - Screaming Frog SEO Spider Tool & Crawler Software | Screaming Frog
There are good tutorials on the tool here - Screaming Frog Guide to Doing Almost Anything
Looking for GTM alone won't tell you if Munchkin is being init'd on a page, since people use GTM to enable and disable Munchkin.