How to improve API documentation with Swagger and OpenAPI

Why standardization is critical to API use

Documentation is key to handle a specific API and share any necessary code. In the past, a lack of standards and clear parameters for documenting and sharing required data limited API creation. With an accurate list of all methods, parameters and responses in documentation, developers can better understand the best way to enable key interactions between web services and software components.

Introduced in 2015 by SmartBear Software, the Swagger specification created a language-agnostic standard for developing RESTful APIs. Swagger donated this specification to the open source Linux Foundation's OpenAPI Initiative and was renamed OpenAPI Specification (OAS). This specification makes API functionality explicit; it defines the API's contract and how it interacts with various resources. While developers rely on the OAS for code standardization, they use the Swagger ecosystem to access front-end interfaces, low-level code libraries and API management tools.

Advantages of Swagger's tool sets

Concise and clear documentation is integral to API creation, especially since APIs change and evolve rapidly to handle new services and design features. By explicitly defining an API's resource interaction, the OAS satisfies this need for clear-cut documentation. Further simplifying things, both machines -- which relay instructions -- and human developers -- who design them -- can easily read and understand the OAS.

By design, the Swagger framework works with the REST model for public APIs. RESTful APIs offer a small footprint and use the widely adopted HTTP standard and JSON file format, making them flexible and easily manipulated for frequent updating. These attributes are essential for streamlining RESTful API documentation and for clarifying how an API should perform.

Developers can use the SwaggerUI to create interactive APIs that are easily comprehensible for developers and non-technical end users alike. While teams can use the SwaggerUI for free, as an open source tool, it is also available within the SwaggerHub platform, which offers a number of other tools and features. Find clearer definitions for the different tools in the Swagger ecosystem here:

• SwaggerHub: SwaggerHub, an integrated API development platform, enables DevOps for teams to collaborate on and coordinate the API build process while integrating their preferred tool sets. It also makes documenting and testing services much easier. Furthermore, as design iterations multiply and documentation evolves, teams can use SwaggerHub to ease the intensifying challenge of managing multiple API versions. In addition to easier tool set access, SwaggerHub provides secure access and hosting of OAS definitions as API strategies expand and change.
• Swagger Editor: With this editing tool, developers can create new documentation and design APIs, as well as edit existing ones. The editor instantly evaluates code against the OAS then identifies syntax errors. Developers can also test and validate APIs within their browsers and automatically save these updates to the cloud for easy access. While developers can use Swagger tools with JSON descriptions, the editor also supports YAML.
• Swagger UI: Developers can host this customizable user interface in any server environment and visualize APIs. They can convert an OAS contract and integrate it into an API console in order to interact with and understand a specific API's behavior. It offers a collection of HTML, JavaScript and CSS elements that dynamically generate documentation from an OAS-based API. Using a simple workflow, developers can test APIs and quickly send browser-based requests to determine how an API will respond before writing any code.
• Swagger Codegen: This code generator streamlines the API creation process by enabling developers to generate server stubs and client software development kits. Developers can create selected client libraries using the Swagger UI, in combination with Codegen, and then generate basic code that enables an application to interact with an API. Also, with customized toolchains built around Codegen, developers can quickly convert OAS definitions into code.
• Swagger Inspector: Swagger Inspector is an API testing tool that also executes API requests, validates its responses and generates related OpenAPI definitions. Teams can use DevOps practices to seamlessly call each endpoint and use the associated response to generate OAS-compliant API documentation with Swagger. Alternatively, they can string together a series of calls to generate a full OAS document for multiple API endpoints.

Swagger, OAS 3.0 and beyond

The official release of OAS 3.0 occurred in 2017; it was the first iteration of the specification since its donation to the Linux Foundation. This version solidified its position as the leader of API definition formats, due to high adoption and the amount of tooling that's been developed around it.

Version 3.0 boasts a more modular approach to defining the surface area of an API. This approach provides more versatility when describing the API request and response model. The latest version also reinforces the importance of good schema and component reuse, as well as multipart document handling.

This version also simplified how developers create definitions for API actions. Version 3.0 makes it easier for developers to create definitions that can be reused multiple times throughout an API specification. Nonetheless, developers can continue to use Swagger 2.0 with SwaggerHub, any new Swagger tooling or other supporting platforms, too.