Real time, contextual fact checks have long been considered the non plus ultra by fact-checkers. Attach a warning to a falsehood immediately, the theory goes, and it will cause far less damage. Which is why CNN's unorthodox use of chyrons has piqued political fact-checkers' attention.

In June, CNN used just five letters and two brackets to point out Donald Trump had been inconsistent on whether Japan should develop nuclear weapons. Since then, both CNN and MSNBC have used the technique at least three more times, twice again on Trump and once on his son Eric.

If this is going to become a regular feature in the networks' coverage of the 2016 elections, some guidelines should probably apply.

1. Check Hillary Clinton, too (and everyone else!)

The Democratic nominee has had her fair share of fact-challenged or contradictory statements, for instance about how she handled her emails while Secretary of State. Yet for the moment and to my knowledge she has not been given the chyron treatment from CNN or MSNBC.

Selective use of the chyron allows Trump partisans to double down on criticism of the media as biased.

2. Deliver alternative explanations cautiously

Besides denying the blatant falsehood that Barack Obama literally founded ISIS, CNN introduced in the chyron the alternative explanation that the actual founder was Abu Bakr al-Baghdadi. While presenting the alternative explanation is an important step in effectively debunking a falsehood, CNN's one-liner is itself not completely accurate.

As Pulitzer prize-winning author Joby Warrick noted on The Washington Post, the terrorist group was born under the leadership of Abu Musab al-Zarqawi, even if it was initially known as Al Qaeda in Iraq.

There is a reason why fact checks are often long, hyperlink-rich, blocks of text. Establishing precisely what is and isn't true without being simplistic is a nuanced process. While a full explanation would resemble less a chyron and more a Star Wars crawl, the choice of text used to fact-check should be very carefully weighed. It should undergo a stricter vetting process than the other text occupying that space.

3. Explain what you're doing

I have not seen any explanation by CNN of how, why and when they will be fact-checking in the chyron. Nor did the network respond to my request for comment about it. Yet readers of PolitiFact, The Washington Post's Fact Checker and Factcheck.org can turn to these outfits' respective methodologies to find out how they choose claims to fact-check, whether they reach out to the authors of these claims, and so on.

Will CNN highlight contradictions as well as factual inaccuracies, as it did on Friday morning? Will it fact-check speeches while transmitting them live? Whatever it does, it can't pretend this isn't an editorial choice and as such one in need of a transparent justification.

Correction: the first published version of this article indicated that all four  fact-checking chyrons mentioned above occurred on CNN. In fact, one of them was on MSNBC. We regret the error.