API docs: The seven principles of great API docs and how to apply them
Create great API documentation for your users using these foundational principles
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Create great API documentation for your users using these foundational principles
Last updated
Was this helpful?
Was this helpful?
How important is API documentation?
Sure, web dashboards, Postman collections, and OpenAPI specs each play a role in helping developers use and learn your API. But without API documentation, it’s like unveiling an exciting new gadget, handing over a complex wiring diagram, and saying, “here, have fun!”
So, as the main product experience you offer to developers, your API reference docs must play a role at every stage of the developer journey. They’re your product’s marketing, onboarding, and user interface. Oh, and not to forget, they also need to give your developers the information they need to learn and use your API.
With such a central role to your API’s success, there’s a lot riding on the quality and readability of your docs. And creating API reference documentation that developers want to read is as much a user research, information architecture, and usability challenge as it is a writing task.
That’s why, in this guide, we’ll introduce the seven principles of great API reference documentation and then show you how to apply them practically.
Just want the advice in its shortest form? Here are the seven principles you need to apply when creating API reference documentation that developers want to read:
Clear: Simple language is always better.
Concise: Get to the point quickly. Make it skimmable.
Contextual: Even skimmable docs need context to make them useful.
Complete: Every endpoint, every response, every variation.
Consistent: Format, terminology, and approach should be the same across every part of your reference docs.
Concrete: Use examples. Make it interactive if possible. Explain what it looks like in the context of a real scenario.
Convenient: Meet developers where they are. If you can, find ways to help them without needing to come to the docs at all.
Now, let’s look at what that means for how you create API reference documentation.
Knowing your developers, and what they want to do, is the difference between good docs and great docs. Good docs contain all the information your developers need but they’re built around what makes sense to you and your colleagues.
Great docs anticipate what your developers are looking for. And the only way to do that is to understand the needs, preferences, and goals of the people working with the product you’re documenting.
If you’re already confident of who your developer audience is, you can skip to the next section. Otherwise, here are three steps to better align your docs with developer needs:
Create documentation personas: Define who your audience is and the jobs they want to get done.
Interview developers: Identify the specific challenges they face and the context in which they use your API.
Collaborate with internal teams: Consult with support, DevRel, and product teams to understand the recurring questions developers ask and the common roadblocks they encounter.
How does this tie back to the seven Cs? Research of this type directly supports being clear, contextual, and convenient, helping you provide the right details, in the right context, exactly when developers need them.
Calling it “documentation” downplays just how important your API docs really are. Developers use your docs to evaluate if your API meets their needs, to build with, and to troubleshoot when things go wrong.
Knowing that, and with your research data to hand, you can build your reference docs to serve developers based on what they need at different stages of their relationship with your API. And in the spirit of not detracting from the core job of API documentation, that might mean providing unobtrusive but easy-to-find links out to other materials.
By mapping each stage of the developer journey, you ensure your reference docs are clear, complete, and contextual.
Generating documentation directly from your OpenAPI spec saves time, reduces errors, and ensures consistency. Auto-generated docs pull from the latest spec, keeping your documentation in sync with the API itself.
Reduce manual effort: Auto-generated docs lighten the workload, allowing your team to focus on enhancements rather than routine updates.
Minimize errors: Direct generation reduces inconsistencies, ensuring that every endpoint, parameter, and response is accurately documented.
Achieve complete and consistent docs: So long as your OpenAPI spec is thorough, your docs will reflect the API fully and consistently.
But, of course, that’s just the foundation layer. There’s work to be done to create truly great docs from an auto-generated starting point.
Sometimes the best reference documentation is the kind that developers don’t even have to visit. Instead, it’s built into the API itself.
Take error messages for example. Although your reference docs should provide comprehensive error information and troubleshooting, you’ll provide a better overall developer experience if you can work with your colleagues in engineering to make error messages specific and actionable.
Here are a few examples of good error messages:
400 Bad Request: Missing required 'user_id' parameter in the request body
403 Forbidden: API key is inactive or lacks necessary permissions for this endpoint
422 Unprocessable Entity: The 'start_date' must be in 'YYYY-MM-DD' format
Each error response gives developers the context they need, right where they need it, saving them time and minimizing friction.
By meeting developers in their workflow, you make your documentation convenient and contextual.
Developers come to your docs to get a job done. Even if your API is exactly what they need, a frustrating user experience can make them look for alternatives. Great UX means making your docs easy to navigate, so developers can focus on building — not on finding information.
With the right user experience, your documentation can be clear, concise, and consistent, helping developers quickly find the answers they need with minimal effort.
One specific aspect of the user experience is allowing developers to get answers fast. They’re goal-oriented, especially when debugging or implementing for the first time. Making your docs searchable and interactive reduces friction.
Precision matters: Ensure your search function returns relevant, precise results. This means indexing key terms, structuring headings clearly, and using semantic HTML for effective searching.
Boost findability: Accurate metadata and well-organized content improve both SEO and usability, helping developers find what they need quickly.
Consider LLM chat: An LLM-powered chat tool can allow developers to ask questions conversationally, receiving specific answers without needing to navigate through multiple pages.
Searchable, interactive docs enhance clarity and convenience by helping developers find complete information quickly. This supports a contextual experience, delivering just what they need, right when they need it.
Examples matter. They turn a dry list of endpoints into something concrete. Whether it’s a cURL command or a sample of Ruby, C#, or Kotlin, examples show developers the shape of your API and make it easier to imagine how they’d put it to use.
When something goes wrong, the last thing developers need is a frustrating search for answers. Comprehensive error documentation saves time and makes troubleshooting easier, but only if it’s well-organized, thorough, and actionable.
Document error codes thoroughly: List each error code with clear, specific explanations. Avoid vague messages; tell developers exactly what went wrong and what steps to take.
Provide troubleshooting tips: Go beyond error codes by offering practical advice on handling common issues. Include step-by-step guidance to help developers resolve problems quickly.
Link out to additional resources: Reference documentation might not be the place for detailed architectural insights or best practices, but linking to these resources can help developers avoid or better understand errors.
Clear, detailed error handling makes documentation more complete and improves clarity, helping developers resolve issues without unnecessary guesswork.
APIs evolve and with each new version you need updated docs.
That’s because upgrading from one API version to another can be a significant engineering and testing task for the developers working with your API. So, you’ll continue to have people using older versions of your API for as long as you make them available.
And because your docs are your product experience, you can best serve your developers by providing documentation for each live version of your API. That way, developers can find accurate, relevant information, no matter which version they’re working with.
Otherwise, you risk confusion and unnecessary errors, especially if you have people still working with an older version while your docs cover only the latest release.
Versioned documentation supports consistency and completeness by ensuring all active API versions are well-documented. Clear communication around changes also improves clarity, helping developers confidently work with any version of your API.
So, if your documentation is as much a part of your product as the API endpoints themselves, then it should also be a core part of your product’s software development lifecycle (SDLC). In other words, an API feature isn’t done-done until the documentation is published.
Building docs into the SDLC ensures completeness, consistency, and clarity by keeping them accurate and reflective of the latest API changes.
Real-world feedback from developers is essential for keeping your documentation relevant and effective. It highlights gaps, inconsistencies, and areas for improvement that might otherwise go unnoticed.
Feedback loops help ensure that your documentation stays complete, clear, and responsive to developer needs, keeping it valuable over time.
Creating great API reference documentation is more than listing endpoints — it’s about building a resource that’s clear, concise, complete, consistent, and concrete for every developer’s needs. But how can you achieve all this while staying on schedule and ensuring accuracy in your documentation workflow?
With GitBook, you can put these principles into practice efficiently:
Generate and update docs straight from your OpenAPI spec to keep them accurate and consistent.
Add interactive API blocks that let developers experiment and see real-time responses.
Collaborate with subject matter experts, reviewers, and other members of your team using branch-based workflows.
Publish documentation for each version of your API and make it easy for developers to navigate between them.
Publish your API docs alongside your primary user docs, changelog, guides and more with site sections.
Collect feedback directly within the docs, keeping your documentation in sync with real developer needs.
By using GitBook, you’ll create developer-friendly API documentation that’s easy to use, maintain, and improve. Get started with GitBook today to deliver docs that developers will rely on and return to.
Organize your content thoughtfully: Structure your reference docs to make information easy to find. Think about how they connect with tutorials, how-tos, and explanations, and consider frameworks like Diátaxis to address different needs at each stage.
Keep style and layout consistent: Use clear headings, a simple layout, and uniform terminology. The goal is to make your docs skimmable, reducing the time developers spend searching for answers.
Stay out of the way: Signpost important sections and maintain a natural flow that doesn’t distract from the task at hand. Developers should feel like they’re solving problems, not navigating an obstacle course.
Good reference docs have examples in the languages developers are most likely to use with that API. Great reference docs provide interactive, try-it-out blocks where they can edit code and see realistic responses.
Maintain versioned documentation: For every active API version, provide a corresponding set of docs. This allows developers to toggle between versions easily, finding exactly the right information for their needs.
Highlight breaking changes and offer migration guides: If an update introduces breaking changes, make them clear. Providing migration guides helps developers adapt their implementations with as little frustration as possible.
Use tools to help: Tools like GitBook’s site variants make it easier to manage documentation updates, allowing teams to align docs with API changes in real time.
Docs as code: Treat documentation like any other part of your development work. Use branch-based workflows to review, test, and approve doc updates just like code changes, keeping everything aligned.
Assign a documentation owner: Give someone (or a team) responsibility for API docs to maintain quality and consistency. This ensures that documentation gets the attention it needs and keeps updates on track.
Collaborate across teams: Involve developers, product managers, and others in the documentation process. Each can contribute another dimension of insights that help align the docs with developer needs.
Add direct feedback options: Documentation can almost always be improved. Adding features like page rating buttons makes it easy for readers to share feedback. Some teams take it further by enabling blog-style comments directly on documentation pages.
Review support tickets for common issues: Regularly analyze support tickets to identify frequently asked questions or recurring issues. These patterns often reveal documentation gaps that need attention.
Conduct usability tests: Test your docs with actual developers to understand how they navigate and use the content. Usability testing can uncover hidden pain points and guide improvements.