Amazon made $2.2 billion in "other" revenue in the second quarter, up from $2 billion in the previous quarter. "Other" is primarily made up of Amazon's ad business.

The e-commerce giant continues to make inroads in advertising — and agencies say they're getting access to more sophisticated ad-buying tools.

Interestingly, Eric Heller, the CEO of Amazon-focused and WPP-owned Marketplace Ignition, said the agency was seeing a boom in branding dollars shifting to the platform.

Amazon's ad business continues to surge, raking in $2.2 billion in the second quarter, the company revealed this week. Amazon buckets the revenue into a line item called "other" that primarily comes from advertising.

Amazon reported $52.9 billion in revenue in the quarter, slightly lower than analysts' expectations, while "other" income jumped 129% year over year. The company reported $2 billion in "other" revenue in the first quarter.

During Amazon's earnings call, its chief financial officer, Brian Olsavsky, rattled off three areas it's interested in improving in its advertising business: the "usability" of its tools, product recommendations, and automated offerings.

Measurement is also a priority, he said.

"We think that we're uniquely positioned to show them the direct benefit of their advertising," Olsavsky said of advertisers.

Amazon is clearly cozying up to advertisers — and not just ones that sell stuff

Amazon continues to intrigue advertisers, and the platform is already nabbing bigger budgets, according to Eric Heller, the CEO of Amazon-focused and WPP-owned Marketplace Ignition.

The e-commerce juggernaut is well known for focusing on retailers and consumer-packaged-goods brands that are fixated on direct-response advertising. But that's changing, according to Heller. He said marketers are increasingly shifting brand-marketing dollars over to Amazon, indicating brands are eyeing Amazon for more than experimentation in advertising budgets.

Heller cited billboards and out-of-home advertising as examples of where brands are cutting their spend and moving it to Amazon.

"We're seeing dollars move to Amazon, and I think the reason why is because they're closer to a shopping cart," he said.

Heller added: "Even a year ago, Amazon was this direct-media platform, and I would tell you over the last three to six months we got access to brand dollars because everyone realized 'Why are we trying to win billboards on highways when we're losing when someone searches for our brand name on Amazon?'"

In terms of where marketers are spending those brand dollars, advertisers are specifically savvy in buying headline search ads, a valuable placement that appears at the top of search results on pages.

The agency's research has found that 68% of online-shopping searches in the US start on Amazon, and that when looking at both the US and the UK, 80% of shoppers use Amazon's ratings and reviews when deciding to make a purchase.

It's getting easier to buy Amazon ads at scale

Additionally, Amazon's ad-buying tools have improved over the past year, Heller said. For example, six months ago, Heller's team managed campaign budgets through Excel spreadsheets. Now he's able to bill clients through purchase orders that don't require tying a credit card to individual campaigns.

Rolling out more sophisticated tools mimics how other platforms including Facebook, Google, and Twitter built their advertising fortunes. Amazon's ad-buying platform is likely not nearly as slick as those companies' platforms, but it's clear Amazon is gaining steam and marketers are starting to see results, Heller said.

"We're starting to get API access, and Amazon is focused on making it easier to spend the money that you should be spending," he said.