How to Document Your REST API Like a Pro

REST API is an application programming interface that continues to grow in popularity due to its flexibility and scalability. In this detailed guide, we will outline how to document your REST API like a pro, guiding you through the process clearly and concisely to make things as easy as possible. 

From the basics, what you need to include, and all the way to the tips and tricks, we will provide everything you need to know to create perfect documentation. In addition, we will also discuss tools such as Swagger and RAML that can help optimize the documentation process and improve collaboration. 

5 Key Takeaways

• REST APIs are favored for their simplicity, modularity, and ease of integration with a wide range of applications, offering significant advantages over older RPC-based APIs.
• Effective REST API documentation is critical for governance, seamless collaboration, and to ensure a quick understanding and integration of the API by developers.
• Common issues with API documentation include complex language, lack of examples, inaccuracies, and accessibility only for registered users, which can deter potential adopters.
• Best practices for documenting REST APIs include clear planning, prioritizing important sections, maintaining consistency and simplicity, adding interactivity, and catering to both experienced and entry-level audiences.
• Utilizing tools like Swagger and RAML for documentation, adhering to industry standards, and ensuring regular updates are essential for creating effective, user-friendly API documentation.

Table of Contents

• Why Choose REST API?
• Understanding REST API Documentation
• Documenting your REST API like a Pro
• Writing REST API Documentation: Best Practices
• Conclusion

Why Choose REST API?

In the past, APIs were typically developed around a remote procedure call (RPC), sending a request to a remote server to execute a procedure. To the user, this appeared to work in the same way as a local function but caused issues when an API was deployed on the web due to the connection-less nature of the HTTP protocol. 

A common workaround was using a technology stack that worked in the same way as RPC, helping developers to make the transition to the web faster. However, this also resulted in developers creating inefficient code - the solution is REpresentational State Transfer (REST).

REST is very simple and versatile, and is the preferred choice by many due to its modularity. REST has a relatively easy learning curve, especially when coding in a general-purpose programming language such as Python. 

Providing all the functionality a developer needs from updating individual modules, integrating payment gateways, and generating documents without having to write lines and lines of code. For individual devs, this is a breath of fresh air but can be a lifesaver for big organizations looking to write new or rework old software. 

How does REST work?

REST is a software architectural style that uses simplified HTTP calls to communicate between multiple machines. A less complex method when compared to RPC or CORBA. With REST, all calls are message-based and rely on HTTP to describe them in a straightforward request/response system.

This works effectively because the API is not reliant on client-side technology and can be accessed from a range of applications and devices. This makes it possible to design infrastructure that is not tied to a client-side stack long-term and can easily be repurposed or scaled.

REST also supports caching and is completely stateless. Likewise, REST APIs enable a decoupled architecture where the front-end and back-end can be developed independently using the most suitable technologies, allowing for full stack hosting and making the devs’ lives easier. This is achieved by REST providing the necessary infrastructure to host and run these diverse technologies together, allowing for greater flexibility in technology choices and easier updates or migrations.

Understanding REST API Documentation

REST API documentation is a reference document that explains how to use the API, effectively a technical manual that contains all a developer needs to know about what the API does and how it works. This includes elements like individual endpoints and parameters, error messages, and detailed comments and instructions about how the API is implemented. 

API documentation is not only essential in terms of governance but it is also vital for ensuring seamless collaboration, especially if a new developer joins the project. In addition, there are plenty of ready-made templates available online. This can be useful because an API is likely going to be used for many different software products, meaning more people, other than the initial developers, need to know how it works. 

Detailed REST API documentation reduces the amount of time needed to understand an API, increasing productivity and reducing deployment times. This allows it to be used for a range of use cases with minimal obstacles, making your API more accessible. 

Why Developers Dislike API Documentation

Typically, if a developer does not like a specific API, it’s probably because of its sub-par documentation. Even if the API is a great piece of software, poor documentation can cause issues when trying to integrate it with other software products. 

Common pitfalls when it comes to API documentation include:

• Documentation is sometimes hard to follow as it isn’t written in simple human language. This is a common issue when documents are auto-generated or the comments have been rushed by the developer. Generative AI can be extremely handy when creating API documentation but it is no replacement for clear and informed explanations written by the developer. 

• API Documentation can also be tedious to follow if there are little or no code samples provided. This can often be the case when documentation is overly descriptive instead of providing relevant and easy-to-understand examples. 

• The documentation can be too long, contain inaccuracies, haven’t been updated in a long time, or have been moved so it can no longer be found. Meticulously building an API but failing to create appropriate documentation, not keeping it up-to-date, and not ensuring it is easy to find online is counter-intuitive. 

• Finally, some documentation is only available to registered users which can deter developers who want to gain an understanding of the API before committing to use it. 

Documenting your REST API like a Pro

Now the usefulness of REST API documentation has been established, we can focus on how to create exceptional documentation as simply as possible. In this section, we will break down the process into five key steps, from the initial planning stage to writing for a wider audience. 

1. Planning your REST API Documentation

Planning is essential when creating winning API documentation, Make sure you know who the documentation is aimed at so you can decide on how it will be structured, what language and tone to use, and how it will be formatted/ designed. Once this has all been established, the writing process will go much smoother, with a clear outline to follow. 

During the planning stage, you should ask yourself two key questions:

• Who is going to read your API documentation?
• What is the intent of the reader?

These questions will help you determine the overall purpose of the documentation so you can make it as useful and readable as possible. With a clearly defined structure, your documentation can cover all bases so that the needs of the user are met. 

2. Decide on your most important sections

All sections within a REST API document are valuable, but some are more important than others, and some are mandatory. Before writing the document you should establish which sections are most crucial to your readers. This could include:

• An overview that describes what the REST API does and what it can be used for
• How authentication details can be acquired to use the API
• A glossary of error messages that may be encountered when using the API
• What resources are needed to be able to use the API?
• A Terms of Use section

A section focused on cybersecurity is also recommended, with many APIs targeted by hackers in an attempt to gain unauthorized access to personal and financial data. With an average of 2,200 incidents per day, worldwide, it cannot hurt to provide developers with some guidance on how to better protect data. 

3. Avoid jargon and ensure the document is consistent throughout

From the first page to the last, your API documentation needs to be consistent in terms of its structure and its use of terminology, so as not to confuse the reader. Try to make the document as uniform as possible, ensuring the language used does not change and the code examples follow the same format. Proofreading is essential to determine if any parts of the document are inconsistent, make little sense, or are unnecessary. 

Naming conventions and terminologies should always be the same and you should try to avoid the use of complicated jargon where possible. As mentioned earlier, developers prefer to read the documentation in simple, straightforward language. It is also good practice to be consistent when using standard conventions such as HTTP verbs, status codes, and other items that are referred to throughout the document.

4. Include Interactivity

While reading API documentation, developers are likely to test various elements to make sure they work as they should. Life can be made much easier for the developer by adding interactive sample codes in popular programming languages such as Python or JavaScript. This can ease the learning curve of the API to help developers understand its capabilities quickly. 

Test data can also be included in the documentation which can be used to run requests, allowing developers to see the various responses. Libraries and software development kits (SDKs) can also be included to assist developers, while entry-level readers would benefit from a simple ‘getting started’ section and easy-to-follow tutorials. Tutorials could even be delivered in video form. 

5. Writing for an Entry-Level Audience

Not everyone reading your REST API documentation will be an experienced developer which is why it is important to cater to entry-level readers too. This audience could include beginners in the software development field, marketing specialists, journalists, and less technical decision-makers within an organization that may find the API useful. 

In many cases, documentation is created by a technical writer rather than the developer as a good technical writer can easily explain complex aspects of a REST API in a simplified way. However, even an experienced technical writer can fall into the trap of using jargon or neglecting the API’s entry-level audience. 

Writing documentation with the low-to-zero experienced user in mind is recommended. And, if you feel the need to go into more technical detail or include more complex examples, this could be covered in an ‘advanced user section’, to show the full potential of the API and even showcase gradual improvements as you implement them. 

Writing REST API Documentation: Best Practices

By following the five steps outlined in the previous section you are well on your way to creating documentation that goes beyond being fit for purpose. But, API documentation can be futureproofed and made even more digestible by following these tried and tested best practices.

Adhere to Industry Standards

Most API documents follow a standardized industry layout to easily organize large quantities of information and data so the reader can navigate it easily and find what they are looking for. Deviating away from industry standards can result in documentation that can be confusing, unstructured, and perhaps even unreadable for some users.

Common features in an industry-standard layout include:

• Stick to a three-column layout, using the third column for code examples when necessary. 
• Use a dynamic layout so the reader can easily jump to specific content and add bookmarks. Dynamic documents are also much easier to update and maintain.
• Improve navigation further by enabling sticky contents, allowing the reader to seamlessly navigate from section to section.
• Use contrasting colors for syntax to ensure individual components within code examples stand out and can easily be differentiated from one another.

Use Helpful API Tools

It’s advised to use API tools where possible to automatically generate content and format your documentation. Swagger, for example, generates documentation based on your API definition and makes it possible to create the definition if you haven’t already. Swagger also features an advanced versioning system that makes it very easy to track all API iterations within your REST API document. 

Another great tool is RESTful API Modeling Language (RAML) for describing static APIs, including RESTful APIs. When creating documentation, RAML encourages the use of best practices, promotes reuse, enables discovery and pattern-sharing of the documentation, and more. RAML is also completely open-source, with many third-party tools built to work alongside it. 

In the modern digital world, it is also impossible not to mention AI, which can speed up countless tasks, including the creation of documentation. Generative AI can be extremely useful for research purposes and for creating generic code that can be edited and improved, making the documentation process less time-consuming. 

Keep API documentation regularly updated

A common issue with API documentation is that it is outdated, with no process in place or no one taking responsibility for the upkeep of the document to include recent changes. This can be infuriating for developers.

To ensure your REST API documentation does not become outdated you should:

• Only include updates once they have been proofread, formatted, and properly finalized so they don’t appear as a rushed, lazy inclusion.
• Review the document regularly and remove deprecated data. This could be scheduled every few months, but reviews can also be carried out on the back of user feedback if any errors or inconsistencies have been identified.  
• Utilize API analytics tools, like IBM’s API Connect to improve your documentation. These tools can highlight which endpoints are used the most so the document can be edited to give more focus to key areas. API analytics can also identify common use cases, giving you more insights into who is using the API. 

Conclusion

Creating REST API documentation can be a laborious task, but by following best practices and utilizing tools such as Swagger and RAML. The process can be streamlined to ensure the document is not only created quickly but is also highly readable and meets the needs of the user. From focusing on the entry-level user to adhering to industry standards, writing REST API documentation like a pro is easier than you might think.

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