How to Write API Documentation in 5 Simple Steps 

Updated on December 22nd, 2021

Technical writers have to work with several different types of technical writing tasks. Some tasks are more technical than others and require additional knowledge, skills, and qualifications, and they usually pay better. That's why many technical writers end up wondering how to write API documentation. 

Writing API documentation is highly technical and among the most complex technical writing tasks. It requires direct knowledge of the subject matter and prior experience in IT. 

As a result, most organizations only look for technical writers to write excellent API documentation. 

This article will go over what API documentation is and how to write API documentation for your organization. 

Let's get right into it. 

What Exactly is API Documentation (API Docs)? 

API is an acronym for Application Programming Interface; it's a software intermediary that connects and allows two different applications to talk. An API can be complex software or even something as simple as using a social media application. 

Similar to how products and services have instruction manuals and software documents, APIs have reference documents that outline how to use that API. Any such reference documentation is called API documentation, and it's a complete technical manual about the API in question. 

The API documentation starts with all the information related to the services offered by the API. It also mentions how to use various elements, endpoints, and parameters. Where applicable, the documentation also delves into the right implementation instructions in different cases. 

In any case, the API documentation is part of the API management process, and a good API documentation policy is bound to help in API governance. 

Documenting each aspect of the software and what it does is crucial in software development. Therefore, API documentation is essential when developing any software or API, whether it has a simple functionality or a complicated one. 

Furthermore, typical APIs help developers sync and transfer data between different software products more easily. To understand this better, APIs are what help you sync your data between different apps on your computer and mobile phone. 

As a result, the API reference documentation helps the developers of different software understand how to incorporate the API better. That helps them avoid any unnecessary programming obstacles and develop a more user-friendly experience for the final user. 

How to Write API Documentation: A Step-by-Step Guide 

Writing great API documentation can be hard, but you can nail it down pretty well if you follow a set of rules and steps. In any case, it's crucial to have a good understanding of the API and APIs in general. That means you should have some knowledge of programming languages, such as HTML, Java, JavaScript, and more. It's best if you have some developer experience, along with some technical writing experience. 

Furthermore, you should also have good communication skills to continually communicate with team members and developers. You can check out some API documentation from major companies, such as Microsoft, to better understand the format and content. 

However, the best way to write great API documentation is to use the right API documentation tools, use templates, and follow a step-by-step process. 

When you've set yourself up with the first two, you can start following the steps laid down below. 

Plan for All Your API Docs 

The first and foremost step is to plan out your API documentation process. If you don't develop a complete plan and set up a schedule, there's a good chance that you'll either miss out on key points or miss your deadlines. 

Before you start REST API documentation, you should have a good idea of why and whom you're creating the docs for. Understanding your audience and their needs are crucial to planning the documents. That's because it will help you decide on your documentation's structure, language, and overall design. 

For example, you should have a plan and idea for different endpoints, parameters, authentication, curl, JSON, data types, OpenAPI specifications, and more. You also need to figure out if you're using RESTful APIs or others. 

Furthermore, you have to learn about the API itself, whether web APIs, payment APIs, or others. You will also have to consider what API documentation tools you will use, such as Twilio, RAML, Swagger UI, Stripe, and more. You can also consider using online sources and tutorials from sites like GitHub. 

It's best to familiarize yourself with different aspects of APIs, such as Markdown Syntax Documentation, Software Development Kits (SDK), interactive code samples, and open-source information. 

To make sure the API works appropriately for people with the API documentation, you'll have to look at the API blueprint, API design, and API key. 

After all that, you will completely understand the scope and purpose of the API documentation you need to write. 

Understanding all these concepts and developing API documentation with the user experience in mind will help you plan well. 

Include All Critical Sections 

Each API document needs to have some fundamental sections, whether you consider them important or not. These sections improve the document's readability and help people adopt the API better. 

The following are some of the important sections in most API documentation templates. 

  • Overview – The overview section is a summary of the API and its function in one easy-to-understand paragraph. After the header, the opening section is the most important part of the onboarding process. Therefore, it's crucial to mention all the best abilities of the API in the overview. If you're able to grab the reader's attention with the overview, then you've already written a great API document. 
  • Authentication – Some APIs require authentication, and in those cases, you need to explain how to get the access key. It's critical to get this section right because authentication can be one of the biggest obstacles to API success. 
  • Resources – The resources section is the main body of your API document since that section is more likely to be read. Users typically learn about the resources, requests, responses, and more. Each aspect should be detailed, including the endpoints, parameters, and more. 
  • Error Messages – Everyone is bound to get some error messages when using the API. Therefore, the user must understand each error message, its reason, and potential solutions. This section is extremely helpful in first-use cases where someone is using an API for the first time. 
  • Terms of Use – This section is for legal purposes and helps double as a legal agreement. It should detail the rightful use of the API's services, terms and conditions, best practices, rate limits, and usage constraints. 

The sections mentioned above are crucial for all API documentation. 

Stay Consistent and Avoid Complex Jargon 

When you've figured out the sections and start to write the API document, you need to make sure you're consistent. That means you can't use different terminologies, formatting, and reference points throughout the document. 

You need to create uniformity with your content, including information, knowledge, formatting, and language perspective. The best way to ensure consistency is to proofread each section after writing it and then proofread the entire document once complete. At that point, if you notice any sections are difficult to understand and read, either edit or remove them completely. 

Furthermore, it's important to avoid any unnecessary complex jargon. It's best to keep all your terms universally acceptable so that everyone can understand them easily. If you can, avoid using technical jargon unless it is necessary. 

If you're able to convert all technical jargon into easily understandable words and sentences, you're already doing a great job with technical writing. The idea is to write something that resonates with the user and helps them understand complex aspects. 

It's best not to assume that every person who reads the API document understands all there is about APIs. Therefore, keep the language consistent and straightforward so that even first-time users can quickly grasp all the concepts. 

Make Use of Interactive Examples and More 

When you write a block of text, there's a good chance people will avoid reading all of it. You have to keep your readers engaged, and the best way to do that is by including interactive sample code and demos. 

Doing so will help understand the API documentation better because the reader will be applying what they're reading in real-time. Eventually, it will reduce the learning curve of the API in the long run. Furthermore, it may also help users understand any new features that may pop out. 

Other than that, you can include various helpful resources in the API documentation. The extra resources and information will help the users understand the API better and use it more efficiently. 

For example, you can include a quick guide that could serve as a starting point to understand the API's features quickly. 

Furthermore, you can include SDKs, libraries, and tutorials to help users integrate. 

Maintain All API Documentation 

While you may have figured out how to write API documentation, most people overlook the fact that maintaining those API docs is just as important. 

It's crucial to ensure all your documents remain accurate and up-to-date. Obsolete API documentation will lead to frustrated users, reduced retention, and will increase the likelihood of wrongful use of the API. 

It's not hard to continually maintain your API documentation; you can do the following to make sure it stays updated. 

  • If any new features have been added to the API, ensure all relevant information appears in the documents. A good practice is to release another version of the API documentation. 
  • Any features that have been removed or integrated need their descriptions modified. If a feature is removed, mention it in the document, along with the reasoning behind the removal. 
  • As a writer, use any meaningful feedback to improve the quality of the API documentation. You may have missed out on some things or were unclear; therefore, it's best to use the feedback to make continuous improvements. 

When you set up a process of maintaining your API documentation, you officially know how to write API documentation. 

How to Write API Documentation Moving Forward 

Once you understand what it takes to develop great API documentation and start following all the steps, you will develop a process. You can include any need-based steps according to your industry and organization to improve the process. 

In any case, as a technical writer, once you've developed the entire process, you will always understand how to write API documentation for your company and its APIs. That's a critical skill to have as a technical writer that can put you ahead of the competition when looking for jobs. Make sure to gain this skill to bump up your technical writer resume and cover letter.


If you are new to technical writing and are looking to break-in, we recommend taking our Technical Writing Certification Course, where you will learn the fundamentals of being a technical writer, how to dominate technical writer interviews, and how to stand out as a technical writing candidate.