The key deal terms are straightforward: China has promised to buy a heaping pile of stuff from the United States over the next two years, and to make it a little easier for American companies to do business in China. The United States has promised to stop raising tariffs.

President Trump is justified in describing these terms as something new. The United States historically has focused on negotiating the rules of international trade, and then allowing economic conditions to determine the volume. The Trump administration, by contrast, is primarily focused on increasing the volume of exports to China. It wrested from China an agreement to increase its total purchases from $186 billion in 2017 to $309 billion in 2021.

There’s no real precedent for that kind of rapid increase in trade with another country, and some analysts doubt that China even intends to fully meet the terms. The bigger issue, however, is that even if China comes through — even if America ships a lot more soybeans and natural gas, and sells more financial and technical services — the United States may not benefit.

The deal is structured to reduce the annual trade deficit between the two countries, allowing Mr. Trump to claim a political victory. Mr. Trump views trade as a competition between the United States and China, and he follows the balance of trade in much the same way that sports fans keep track of the score. But bilateral trade balances are economically insignificant. It doesn’t matter if a nation has a trade deficit with China if it has offsetting trade surpluses with other nations. And in this case, much of what China has agreed to buy from the United States would have been sold to other nations. Increasing exports to China doesn’t mean that the United States is increasing overall exports. The economic benefit may be quite small.

The commitments also end after two years. China is making no promises beyond 2021.

There are important downsides, too. The United States is essentially demanding that China shift trade away from other countries, some of which are American allies. The United States also has long pushed China to develop a more market-oriented economy. This deal, by contrast, encourages China’s government to orchestrate purchasing, most likely with a heavy reliance on the very state-owned enterprises the United States has long sought to constrain. The short-term benefits could come at the expense of America’s longer-term interests.