Insights from my Software Engineering Radio interview with Scott Kingsley

Introduction

In a recent episode of the Software Engineering Radio podcast, I interviewed Scott Kingsley, the VP of Engineering at SmartBear. Our conversation focused on the Swagger ecosystem, which is a family of open-source and commercial tools that helps engineers design, document, and test APIs. Building on the OpenAPI specification, the Swagger Editor helps you define an API, the Swagger UI makes it easy to explore that API, and Swagger CodeGen turns a specification into server stubs and client SDKs. Scott also shared some striking numbers about how widely this tooling is used: the three main Swagger UI distributions saw nine million downloads in a single week, and SmartBear manages more than 1.7 million APIs for its customers. I’m thankful that Scott took the time for this interview and I hope you really enjoy it!

Insights

Before you listen to the full episode, please check out some of its insights:

What is the relationship between the Swagger ecosystem and the OpenAPI specification?

“So, the OpenAPI initiative is a highly collaborative effort with experts across all industries, really anyone interested in the advancement of APIs and API functionality. … Now for SmartBear, we’re responsible for building tooling, both open-source and commercial on top of that. … And when it comes to open-source versus commercial, if we don’t build it in open-source first, our commercial products aren’t going to work either.”

What is the trade-off between API design first and code first?

“one is just unlocking parallel development. So, I love that analogy of building a bridge from both sides and you’ve got that contract in the middle and that contract is what’s going to ensure that they’re connecting in the right spot rather just hoping that they do. But even worse than that is only one side can start and the other side other teams just waiting and waiting and waiting until it’s done. … And so, it really can be an accelerator in terms of teams if you’ve got distributed teams that are dependent on each other.”

How do you ensure that a team builds a consistent API?

“Don’t let each team decide what to call a field. You can end up with like really a mess across your whole APIs if there isn’t some sort of governance or oversight into them.”

How does bi-directional contract testing protect the consumers of an API?

“…bi-directional contract testing is built around the premise of the provider says what it does, all of your consumers say how they’re using it and then anytime you make a change you can see if that change is actually going to break that relationship between the provider and the consumer. … Well bidirectional contract testing is going to catch like oh yeah, that’s a totally safe change to make because none of your consumers are using that field or here’s the two out of the five consumers that are using that field.”

How much of the work of writing an API specification can AI do?

“…one of the easiest things that we’ve done is create a natural language form for creating an API from scratch. And so, say an engineer working with their product manager to define the requirements, the API, what it should do, they can then take that, paste that into Swagger studio and then it’s going to go and generate your spec. But not only is it generating your spec, it’s going to do it following your standardization and governance rules that you’ve created and it’s going to conform to that out of the box. So, right away you’re going to get an API that comes back, that’s maybe it’s not a 100% perfect, but 85-90% of that work is all done for you and now you just kind of need to review it.”

What is an MCP server and why does it matter for APIs?

“I think it was late 2024 because Anthropic came out with the concept of MCP servers and this was a way to extend an LLM and give it access to information that it wouldn’t normally have. … it now can access the tools and APIs that you’ve given it to in that MCP server. … And in early 2025 this became a standard that just every vendor started implementing. … It really was a game changer kind of for like getting the latest and newest information available to LLMs.”

How do you publish an MCP server for an existing API?

“if you’re building and managing APIs and Swagger Studio, literally at the click of a button you can click the button that says generate MCP server, it’s going to bring up a window with a list of the endpoints from that API you choose, which endpoints do I want to expose as MCP tools?”

Listen

In conclusion, if you’re interested in learning more about the Swagger ecosystem and how it supports the design, testing, and documentation of your APIs, I highly recommend that you listen to Scott Kingsley on the Swagger Ecosystem from Software Engineering Radio! You can find it on your favorite podcast player, Apple Podcasts, Spotify, YouTube, or listen to it with this handy podcast player.

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