I like Mark Summers take:

Trump declares victory over Trump: Mock threat to impose tariffs on Mexico gets mock solution

Donald Trump has agreed to not do that thing he was going to do so … victory! On Friday evening, Trump declared that he had “signed an agreement with Mexico” under which Mexico will “take strong measures” to reduce immigrants crossing the border into the United States. And because of this agreement, Trump will “indefinitely suspend” the tariffs that were set to take effect on Monday.

Mexico has supposedly agreed to disperse more of it’s own national guard along immigration routes, and along the border with Guatemala in order to turn back refugees before the reach the United States. It has also agreed that some immigrants waiting on asylum claims will remain on the Mexico side of the border, even though that means they won’t have access to attorneys or courts where their asylum claims are being heard. Mexico did not agree to changes in asylum rules that would have limited which immigrants were allowed to apply.

Whether any of this will make any appreciable difference isn’t clear. But it doesn’t have to be. When Trump issued his tariff threat on May 30, he didn’t provide any goals, any numbers, any rules, or even guidelines. He made it clear that he was the sole judge of whether Mexico was doing enough to evade his wrath, and that he could change his mind at any time, for any reason.