Sometimes when watching anime reviews, various reviewers will say a series has a read the manga ending. From context, it appears to mean the anime is incomplete, there will be no sequel, and if you want to know what happens, you have to literally read the manga. This is obviously used with a negative connotation.
I'm sure that usually this is not a planned result; due to whatever reason there ends up being no will or resources to do an additional season. What I am curious about is the alternative case -- is a read the manga ending ever decided up front? I.e. was the anime series considered by the producers nothing more than a marketing tool to drive manga sales? Some reviewers give that impression, but I wonder if there are documented cases where it has been literally part of the plan from the beginning.