Does what it should.

Developers, can you please make this compatible with Firefox for Android? Not sure what that means, but it says it's not compatible.

Just fantastic: goes to the official Pinboard add URL page, prefilling just the URL and title. Similar extensions have created their own inferior UI for tagging (prefilling the description, messing up font sizes, lowercasing tags and more). The only thing which would be a useful change would be to close the tab once the bookmark has been successfully added.