If you develop software today, chances are you are developing Web APIs as well. But while you might not be a company like Facebook or Amazon that both run a huge public API programme, there is still a high chance you are building APIs for your customers to integrate to or even just for internal use.

In these cases, your software development lifecycle and server operations involve APIs. If you are still not using a definition language for machine-readable API specifications, such as OpenAPI (formerly known as Swagger), you should definitely consider doing so. After all, APIs are languages for machines to talk to each other. So it makes sense that their process and documentation is written in a way that machines understand and participate in as well.

There have been many efforts to allow machine-readable API descriptions, some based on language-specific code annotations and some as standalone specifications. However, none have the versatility and wide support from many different vendors without lock-in or preference for specific tools that OpenAPI enjoys. The specification is maintained by the OpenAPI Initiative and is available on GitHub.

Here are 5 reasons why you should consider using the OpenAPI specification.

1. Collaborate on API design

An API is a contract that all parties, servers and clients, need to follow in an exact manner. Changing such a contract is always difficult. This makes the design stage of an API very important, and multiple stakeholders should be involved in it. As a result, the ability to collaborate on API development smoothly is of utmost importance, to ensure consistency and efficiency.
OpenAPI definitions, like other spec formats, are formalised plain-text documents that can reside in a repository, e.g. on GitHub, just like code. As a result, everybody can enjoy the structured approach that versioning systems like Git enforce, and documented history of the design phase.

2. Save time and avoid errors when writing code

Writing code always takes time. There is a chance that bugs creep in, and some parts of it may admittedly be boring boilerplate code. This not only causes errors, but it also makes work meticulous for developers. This can be avoided with OpenAPI as standard, or customised toolchains can convert OpenAPI definitions into code, saving time and effort.

3. Assess and ensure quality

An OpenAPI definition is machine-readable and, if you follow an API design workflow, it is the single source of truth of your API. This means that every part of your system can be tested against the specification. In larger API deployments, an API gateway running in front of an API implementation could inspect incoming and outgoing traffic to determine whether it conforms with the specification. This ensures your APIs are always up to standard, reducing the risks of product malfunction.

4. Generate beautiful and interactive documentation

Even with all types of automation, good documentation for humans is still an important part of every API, because in the end, it’s human developers who have to write and understand the business logic that calls the API. SwaggerUI was the first tool to offer API documentation with integrated test client, so developers could see a list of available API operations and quickly send a request in their browser to test how the API responds before writing any code of their own.

5. Publish and market your API

For public APIs, all of the benefits mentioned above make your API better, and that alone is a big part of attracting other parties to integrate it and build applications with it. Publishing your OpenAPI definition along with your API also allows client developers to use their preferred tools in combination with your API.

6. Bonus one!

Finally, importing an OpenAPI definition into IPaaS providers such as Microsoft Flow opens up your API to non-developers. This broadens the potential audience to be used not by professional developers but also what Microsoft refers to as citizen developers.

OpenAPI definitions play a part in every step of the API development lifecycle. Consider using them from the ground up when designing new APIs to get the most benefits, but even adding an OpenAPI definition, later on, can still be helpful for quality control and for attracting developers to your API.

If you’re in the middle of project implementation and need help in defining, monitoring or publishing your API, contact us today.

Visit our Application Management Services page for more information.