What is API Documentation (and why is it important?)

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Though APIs are created by developers, their end users can range from either being across a whole business, or even further, if the API is public.

So that they can get the most out of it, it’s vital that all these people have an understanding of what the API can and can’t do.

This is where API documentation comes in.

Writing up documentation is never the most exciting part of a project, but for an API, it’s more important than you might think. In today’s article, we’re going to give you a quick refresher of exactly what APIs are, before delving into what API documentation does, and the benefits of having it for your next implementation.

What is an API?

API stands for ‘Application Programming Interface’. APIs let different software applications communicate and interact with each other – accessing and exchanging data easily.

What is API documentation?

Think of API documentation as an instruction manual that goes out to every person using our API. It contains tutorials, code examples, screenshots, and other things that give first-time users clues on how to do what they need to.

Why should I have API documentation?

Developers are highly technically skilled. Because of that, you might think that API documentation is a waste of your time and theirs – especially if they can jump right in and get to grips with it.

However, there are many reasons why having API documentation pays off in the long run:

Accelerated onboarding

By having API documentation in the users’ hands straight away, onboarding will naturally happen faster. Most common questions are answered in the guide provided, so users are at a stronger starting point than without the documentation, meaning onboarding is a smoother process.

Minimised support and maintenance costs

This point follows on from the previous one. Consider this – when developers don’t know how to do something in your API, or have an issue with it, who are they most likely to turn to? If you answered “the support team”, you’re in line with most other companies. Then add multiple developers asking about the same thing, and you’re quickly swamped – both by requests, and by rapidly rising costs.

API documentation makes this spiral less likely. With documentation, the user is empowered to be more proactive, seeking solutions to their own problems themselves rather than going straight to the support team. This has a knock-on effect on their capacity to deal with other incoming cases, in a way that’s better for your bottom line and your task list.

Increased awareness (and adoption) of the API

When we have a good experience with something, it’s human nature to want to tell other people about it. The same principle applies to APIs. The point of documentation is to make your API as easy to use as possible, and if this is the case, there’s a good chance your current users will want to tell their colleagues. That’s a whole raft of potential new customers unlocked, just through taking the time to put together concise, accessible documentation.

Key components of API documentation

Though there’s no ‘one-size-fits-all’ approach to API documentation, all versions of it will have some things in common:


Authentication is key to a safe, secure API – so there are usually multiple ways of doing it. Good APIs will have all of them outlined clearly in the documentation.

Rate limits

A rate limit is the number of times you can send a request to an API in a given period of time. These constraints need to be clearly stated in the API’s documentation and are typically part of its Terms of Use (which is, in itself, an important part of API documentation).


As your consumers will be using APIs all the time, it’s only right that they can stay on top of the changes made. This is what the changelog does – and it also lets you be transparent about the reasons behind those changes.

Best Practices for API Documentation

In addition to the above checklist of things to include, there are also some best practices you should follow when writing the document itself.

Use clear and concise language

Even if your main audience are developers, they’re ultimately still humans. Too much technical language can alienate the exact people you’re trying to talk to – and make the document feel unwieldy and hard to use. Avoid jargon where you can, and try to balance more advanced areas with easier terms (like a ‘Getting Started” section for novices).

Use examples and code snippets

Including code snippets in your API documentation where you can has two benefits. Not only are they clear illustrations of what your API can do, but they also help users to contextualise this in relation to their day-to-day activities.

Keep it updated

Updating an API can be a task in itself. From that perspective, it’s no wonder that updating the documentation can fall by the wayside. But if you want your documentation to be something that users can consult with confidence, keeping it frequently updated is important. Though smaller changes can go in the changelog, it’s good to scan through the documentation at regular intervals so you can be sure it’s still got everything it needs.

Putting API documentation in place is more than a box-ticking exercise. Having a consistent, readable and up-to-date document impacts both the business using the API and the one supporting it. Done well, it can even lead to a growing customer base – not bad for an instruction manual.

Looking for an API solution? PKF Smith Cooper Systems has two – MRGE and WIRE.

Find out more about them here, or call us on 01332 959008.

Interested to know more about our Sage solutions?

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