And therein lies the key to finding a good starting point for building an API: a clear business goal, preferably one that keeps developers at the forefront.

“The team was built and new management was put onboard,” said Taveau. “The background of most of the team comes from the technology world, hardware and engineering, software architecture… There are a lot of different profiles from very well-known tech companies,” he said, highlighting another key to API success: diversity of technological skills on the team developing the API.

“We started looking at the developer.mastercard.com site and tried to see what content was good, what needed to be reworked, and what we needed to have to make sure we could appease the needs of this non-traditional customer base for MasterCard,” said Taveau. Developers are, after all, the customers of all APIs, and should be treated like any customer, he said. They should be kept happy and be heavily considered when designing a product.

Beginning with existing APIs is another way to quickly get things started, said Taveau. But repurposing previously exclusive APIs has to be done in a way that puts the least amount of friction between you and the developer consuming the data.

“When you work with a large partner, you develop APIs that are kind of one-on-one, private APIs,” he said. “Our goal was really to make sure whatever we published on the website were truly public, open APIs and did not require preexisting relationships with third parties to use them.”

The real heart of the success MasterCard has seen with its open APIs has comes from the fundamental philosophy that underlies the goals of the developers on Taveau’s team. “We see our job as being the voice of the developer inside MasterCard. We define the process to the point that the developer doesn’t have to be a payment expert to implement payment inside an application,” he said.

That sentiment is mirrored by Omar Khan, partner director of program management for Microsoft’s Azure API Management. “A successful API program encompasses developer engagement, business insights, analytics, security and protection,” he wrote in an e-mail to SD Times.

But the APIs don’t stop at payments. MasterCard’s APIs can also be used to find restaurants, discern their open hours, and even to determine if their food is any good. Local customers tend to favor certain joints, after all, and the locals always know where the best food is in any given town. Comparing restaurant receipts with card users’ zip codes yields a listing of the places the locals like to eat, versus those that tourists prefer, or that no one prefers.

The restaurant API is a new one, said Taveau. The local eatery API is “designed for applications to help you when you travel and go to a new city. When you go to a new place, you can pop up OpenTable and see reviews. But what we are doing here is a layer where we can pinpoint, based on our data, if it’s a restaurant preferred by locals or if it’s a tourist trap, based on the zip codes of the customers,” he said.