Wed May 4, 2022

How to Write API Documentation: 10 Essential Guidelines

Laptop, notepad, two phones and other items on a wooden table

As is the way with most programming concepts, documentation is vital. An API might as well be gibberish if the documentation isn’t laid out properly.

Developing easy-to-understand API documentation can be quite challenging. But for those who know the right approaches, it can be a breeze. With only 32% of API providers confident that their API docs are above average, we thought it crucial to detail the best approaches and give you compelling reasons why you should always provide excellent documentation for your APIs.

But first…

Who Benefits From API Documentation?

Your API documentation audience is segmented. As such, it’s important to identify the different groups of people who benefit from your documentation. This will give you insights into serving their needs.


Developers are the people who directly use your APIs. In order to use your APIs effectively, they need to understand how it applies to their use case. Additionally, if they need to run QA tests on the APIs, they require as much information as possible about the APIs. They may need to learn how to access and integrate with dozens, or even hundreds, of the resources you expose.

APIToolkit installation documentation

Studies show that developers have become more confident in API documentation over the years. With the numbers rising, it only makes sense if you provide the relevant technical docs to accompany your APIs.

Administrators and Others

This group of people may never actually use your APIs. They are responsible for identifying resources needed by their teams. Some of them are technical like CTOs, whereas others might be COOs. Ensure your API documentation is written with such an audience in mind.

Lastly, journalists, tech enthusiasts, and other non-specialized people will likely come across your API docs. How do you target them? By writing for the least technical audience.

1. Understand your Users’ Needs

The most important step when creating API documentation is to have a clear understanding of your users’ needs and what they expect from the documentation. Start by researching the target audience for your API, and consider their level of technical knowledge. This can help you design the documentation so that it meets their needs in the most effective way possible.

2. Target the Least Specialized Audience

When writing for a mixed audience, the smartest approach is to address the least technical amongst your readers. Try to answer basic questions, give explanations where necessary, and reduce your use of jargon. Here are a bunch of ways to target non-technical audiences

Tell stories: Utilize case scenarios and make stories around them. This engages every kind of audience and shows your product in action.

Be detailed: It’s important to put in all the important bits of information but you should try to do that in as few words as possible. Have an outline that lets you break concepts down into concise bits.

Be instructional: Let your users know where to begin and where to end. Detail complex pieces of information in clearly outlines steps. Give examples where necessary

APIToolkit installation doc

3. Include Detailed Examples

Examples are an essential part of any API documentation since they make the concepts easier to understand, particularly for those who have no experience with the language being used. When providing examples in your documentation, be sure to include detailed steps and provide full descriptions of what is being done. Provide both code examples, as well as images or screenshots if possible. This will help users better visualize what’s going on and create a more effective result.

Stripe API Documentation Example

4. Point to Relevant Supporting Resources

Your readers want all the help they can get. Don’t be stingy with information. Point to any relevant guides and supporting resources that they may need. Don’t leave them guessing. Some examples of supporting documents are:

A Getting Started Guide: This gives a comprehensive approach to using your API. The goal is to ensure your consumers attain success with using your product.

Interactive Console: A console helps your audience to test your APIs and see results in real time. It’s a simple approach that yields big rewards.

Libraries: Code libraries enable developers to easily call different resources. Access to methods in different languages to work with your API helps developers feel more comfortable working with the API.

5. Show How to Request and Use Authentication Credentials

One of the most important guidelines for writing API documentation is to include instructions on requesting and using authentication credentials. Authentication is an important part of many APIs, but it can often be a complex process that users need assistance with. Provide them with the information they need to request and use authentication credentials, so they know exactly how to access your API securely and safely.

APIToolkit documentation snippet

6. Utilize Industry Standards

Make it easy for your readers to understand your documents; use familiar layouts and designs. If you’re using a document generator then the layout is already decided for you.

Here are some recommendations: Use good contrast: The Web Content Accessibility Guidelines 2.1 (WCAG) recommends a contrast ratio of at least 3:1 for graphics and user interface components (such as form input borders). WCAG Level AAA requires a contrast ratio of at least 7:1 for normal text and 4.5:1 for large text.

Use a dynamic layout: These days, layouts must be easy to bookmark. The use of PDFs and single-page documents doesn’t cut it. Ensure your docs are dynamic and scalable.

Navigation bar: Your navigation bar should stick to the screen. Make it easy for users to switch between pages.

7. Describe Your Request-response Cycles in Detail

Your users should not be surprised by API responses. They should know exactly what to expect from API calls.

Document all possible calls your API could offer in relation to the parameters and responses. Responses serve as a contextual guide for your users, showing when they’re on the right path.

Responses also provide guidance with error messages. Overall this helps your users to succeed. Be sure to cover multiple formats when describing the full sample response body.

Lastly, examples are important. Provide examples in each object that your API is meant to return, together with examples of parameters that consumers can add for a successful API call. API observability tools can help with this.

8. Explain Error Messages Clearly

Errors are an inevitable part of using any API, and it’s important to explain errors clearly in your documentation. This way, users will understand why something went wrong and know what steps to take to fix the problem. Providing examples of common error messages can also be helpful for users to reference when troubleshooting. Be sure to include good descriptions of each error message and provide explanations for why it occurred.

9. Make It Freely Available

Trust me, one thing that really irks developers is gated API docs. Don’t be fooled, gated docs do not increase conversions. Developers and decision-makers want to know what to expect before deciding to use your APIs.

Use as many code samples as necessary. Developers appreciate this a lot. Don’r be all talk and no sample.

Lastly, optimize it for search engines. Your docs are no good if they can’t be found with a simple Google search. Ensure the page is indexed, titled properly, and well described.

10. Update Your Docs Regularly

No one likes an outdated document. Stay on top of this. Update your API docs regularly. Here are some recommendations:

Have a standard process/framework for updates: Incorporate your docs into your API update process. This ensures that as you roll out new features, your docs are ready to be published as well.

Review often: Frequent review of your docs will expose outdated areas. Schedule your reviews to keep your processes streamlined.

Use analytics: Good API analytics will show what endpoints are used most frequently. This will inform your API doc review process, helping you focus your updates on the most used portions. APIToolkit provides detailed analytics and much more. It’s a one-stop solution for API observability and monitoring.

Final Thoughts

Documenting your APIs is just as important as building them. It’s essential to have frameworks and processes that make your API documentation seamless and scalable.

You will have different audiences. Be sure to cater to all their varying needs when developing your API docs.

APIToolkit gives you comprehensive analyses of your API docs to ensure you’re constantly up to date with the information you serve your community.