US President Donald Trump and Chinese leader Xi Jinping agreed to a one-year pause in their economic arms race Thursday in South Korea.

But many of the details, including what exactly China and the U.S. have conceded to each other, remain murky.

It’s also unclear whether the ever mercurial Trump and Xi, known for abandoning deals as soon as they no longer suit his purposes, will follow through on their commitments.

“The real question in trade negotiations, even between the world’s two largest economies, is whether Mr. Trump, and now even Mr Xi, who is ‘on’ to his US counterpart, will both make good on what each promised the other orally,” said Harry Broadman, a former assistant US trade representative in the George H.W. Bush and Bill Clinton administrations. “Businesses and investors would be wise to not hold their breath.”

One person close to the Trump administration, granted anonymity to discuss their analysis of the preliminary details of the countries’ agreement,” said that “on its face, the deal doesn’t necessarily make a lot of sense, in terms of the details that we already know.”

That’s because China, according to Trump, has made significant concessions to the US, including substantial soybean purchases, a one-year suspension of its sweeping export controls on any products containing Chinese rare earths and a vague commitment to crack down on precursor chemicals used to manufacture illicit fentanyl that is sold in the US In exchange, the US has agreed to drop tariffs on China by 10 percentage points, suspend an investigation into Chinese shipbuilding practices and delay a new export restriction rule.