Currently, there are three main competing HTTP API specifications: 1. Open API Specification (OAS) by Open API Initiative (OAI) – based on Swagger 2.0, 2. RAML with MuleSoft as main contributor, and 3. API Blueprint backed by Apiary which was bought by Oracle this year. While all three specifications have their own merits and tools built around, OAS has attracted the main support from the community after Swagger was entrusted to the Linux Foundation in 2015. OAS was supported from day one by 3Scale, Apigee, Google, IBM, Microsoft, and PayPal, among others.
It is not clear how the HTTP API space will evolve in the future, but there are some interesting proceedings taking place lately. One of them is the recent announcement from MuleSoft to join the OAI. Uri Sarid, the CTO of MuleSoft and the creator of RAML, has started to participate in the OAI Technical Developer Community considering that “everyone should support a common format that can at least describe the service model of an API” and that format should be “the one most commonly-adopted today: the OpenAPI Specification.”
I was experimenting recently with the process to create API’s. I fell in love with Apiary due to easy Markdown syntax. I created the specification for a few API’s and even used the mock server built into Apiary.IO. In the past, I had used Swagger 1.x and had some difficulties with the Swagger syntax. I make predictions as part of my job. Just like the weatherman, I don’t get fired if I’m wrong. My prediction is that the OAS with Swagger 2.0 with any extensions dreamed up will be the leading API standard for near future.