Consumers looking for drug coverage information on Obamacare's marketplaces might have found themselves out of luck.

Making the health exchange websites easy to use is widely seen as crucial to the health-care law's success: if consumers can't see what, exactly, they're purchasing, they're a lot more likely to be misinformed and unhappy with the final product.

But nearly four in 10 plans on Obamacare's exchanges didn't provide any details on what drugs they cover, a new report from Avalere Health found. And another 11 percent made it difficult to access drug coverage information.

Provider directories were a bit easier to find, but they still had challenges. About 16 percent of analyzed health plans, for example, didn't provide directories — meaning consumers shopping for these plans couldn't look up which doctors and hospitals are covered in-network.

The federal government, for its part, already plans to make some changes. Starting with the next open-enrollment period, the White House will require health plans to submit direct links to provider directories and drug coverage information. That means consumers should be able to see what doctors and drugs are covered by each plan on the federally run exchange.