Why API Specs Are the Backbone of Successful Development

Learn why API specifications are essential to the long-term success of every application and what you’re missing out on if you don’t have one

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The other day somebody told me about a REST API for some software I use almost daily. I typically use their SDK but jumped at the opportunity to use a REST-based offering. I could quickly hash out POCs in Postman and verify my ideas in seconds.

I’m a big fan of REST and API design. I’ve been an advocate for API-first development for years. So naturally, the first thing I do is try to find the spec. I poke around GitHub for a bit, but no luck. So I asked a maintainer about it, and I was given a single curl statement.

curl -d SOMEBLOB https://{{baseurl}}/data/set/KEYNAME?token\=TOKENHERE

Needless to say, I was a bit underwhelmed. It ended up raising more questions than it answered. What should I expect the data to look like in the response? What was the schema of the request body? What about the content type? Can I sub the token query param as an Authorization header? That path isn't very RESTful. Are there other endpoints I should be using instead?

I tried hitting the endpoint, and it gave me an error. But I didn’t know how to fix it. An example curl statement doesn’t go very far when it comes to troubleshooting.

This could have been avoided had there been a publicly available API spec. You can get by for a while without one as you work to churn out features that help determine product-market fit, but eventually, that will catch up. The user base will grow over time, and people will have questions about how it works and what features are available over HTTP.

Let’s talk about what is involved with API specs and why they are so important for long-term success.

What API Specifications Tell You

An API spec like Open API lists the endpoints, schemas, responses, parameters, security, and base URLs for an API. It takes all the guesswork out of exploring a set of features. Specifications tell you exactly what each endpoint needs, what responses you could receive, and why you would…