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How Significant is Usability Testing for Successful API Design?

Summary of learning

As you start writing the specific steps users need to undertake to achieve their goals, you are putting yourself in their shoes and workflows. If you have to go through many challenges while at it, such as inconsistent parameters, the reason might be that your API’s usability is not good. 

As you start writing the specific steps users need to undertake to achieve their goals, you are putting yourself in their shoes and workflows. If you have to go through many challenges while at it, such as inconsistent parameters, the reason might be that your API’s usability is not good. 

So, precisely what is one of the initial signs that your API might not be what you want? Well, it’s accessed based on how hard technical writers find it to write the documentation about your API. If they do, then things may not be your way!  

After all, technical writers are responsible for providing the proper feedback on usability, especially after you step into the user tasks in-depth, but there are more things to discuss. That’s why in this article, we will find out how vital usability testing is for a successful API design. 

How important is usability testing to create a successful API design? 

Usability testing is directly related 

Initially, we need to identify how usability testing is directly related to a successful API design. In other words, usability refers to how easily users can accomplish their tasks while using a tool. In order to evaluate usability, you need to identify what kind of tasks users want to perform 

with the API. 

The timing 

The best time to start conducting usability testing is at the beginning of a project, so do so now if you still haven’t done that. Moreover, a mistake you should avoid making is doing usability testing for your APIs right before the release date. Instead, do it early on and gather feedback early on in the development lifecycle to make any required changes to the product sooner than never.  

So, after you design your API, it’s time to conduct your usability testing. You can easily generate Mock APIs with many modern tools such as OpenAPI that can be used for your usability testing. If you want to develop first and don’t have mock APIs, you can consider performing usability testing after the development stage. 


The best thing you can do is to identify the types of skills and roles your customers have and create user personas from it after. By doing this, you are getting a customer’s perspective on your APIs and finding the right participants to conduct your usability testing.  

However, what also matters is the type of developers you have to integrate your APIs and start developing a new API. Therefore, you need to pay special attention to the people you wish to hire for this part as it’s just as important. 


If your API design has inconsistent designs, it most likely will make the interface harder to understand and use. In other words, an API should be consistent to the extent that developers can predict. However, in terms of evaluating API usability, there are some things you need to cover. 

Have straightforward endpoints 

When you look at an endpoint, will you have any idea what it returns? You always keep in mind the tasks that users want to accomplish with the API and the terms they use to describe the tasks they wish to achieve. 

Moreover, if you could draw a line between the user’s tasks and the endpoint they need to accomplish a task, your endpoints are straightforward. However, if you can’t do this, users might have difficulties. 

Consistency in endpoint patterns 

Ask yourself if the endpoints are following a consistent pattern or not. Take a second to look at them and see if they follow a consistent format. Does it look like different teams working on other API parts without communication? This isn’t quite hard to distinguish for technical writers. 

For instance, some issues you might run into with inconsistency is an API working for one device type may not work for the other one. As a result, names may look inconsistent, and it may seem quite apparent to others that the same team didn’t work on the APIs. Inconsistency won’t only ruin one thing, it’ll ruin many things and not allow users to find the ‘aha moment’ from the products and services they are using. 

Real-world testing 

Consider how the API will be used in the real world and how that’ll drive new design choices. Of course, product owners will always think that they know precisely how a product should be, but consumers are the ones who make the decisions here. As a result, we can say that any developer who conducted a usability session that didn’t work out has been humbled right after. 

This is the same story with an API and users. Think about what details consumers need and how they may be used. Also, pay attention to your environment. For example, can the API be used with an internal app across a local area network (LAN) or a limited bandwidth on a mobile app? 

Some other questions to answer include: 

  • What is the response time? 
  • Is the current response time suitable for the use case? 
  • How many customers need to be served? 
  • Is the API private or public? 
  • Does the data require any special handling? 

Motivating the issue 

API design may be complex because of the many quality attributes for APIs to be evaluated by stakeholders. The two essential qualities of an API are its usability and its power

So overall, usability shows how easy an API is to learn and how productive developers are when they use it. Moreover, it also means how simple it is and how well the API prevents errors. On the other hand, power is more of the API’s expressiveness and extensibility. 

Even though an API has two essential qualities, usability mainly affects it. Something else to know is that the design of an API requires hundreds of design decisions on different levels, and let’s be honest, all of them can affect its usability. These can be anything from the global issue or overall API architecture, what kind of design patterns will be used, and how the functionality will be organized.  


Yes, versioning. It’s an excellent way to add new features to the API or even change them without breaking any experiences for your users. Furthermore, it’s much more cost-effective than making changes and fixes late in the development phase and, even worse, making them when the API is already in the real world! 

These issues can be avoided earlier in the development phase, and specific changes are much less problematic than others. Here are some things to consider: 

  • Adding new data can be an okay choice, but it’ll depend on the data format
  • Removing existing data is never a good idea and removing an existing endpoint isn’t either 
  • Major problems will arise when you choose to change existing data behavior and endpoints 

After all, ask yourself the following questions: 

  • How many versions will you support? 
  • How will you test different versions? 
  • How long will you be supporting these versions? 

Versions directly affect the transparency in your quality and testing. You can consider using the canary concept where a slow-increasing set of clients are directed to the most recent changes and ensure that these sets of changes are acceptable. Alternatively, you can also consider A/B API testing, which includes deploying a performance tweak to a group of clients to validate and measure improvements. 

API usability testing in a few steps 

In order to learn as much as we can from our tests, we need to prepare. Here are a few simple steps you can undertake to get the most out of usability testing: 

  • Define a task which you are supposed to test
  • Give as much information as needed to begin the assigned task 
  • Find out how you can observe the user when they are using your API
  • Ensure that the user is speaking loud enough when testing your product and explains in-depth what they think about your product
  • Allow questions to be asked in case your users get stuck at some point 
  • Create a detailed report based on test results 
  • Derive tasks from your observations 
  • Share your observations with your team 

Wrapping it up 

Well, that’s all in this article. These were our tips and tricks on how usability testing directly affects a successful API design. Moreover, you must address any issues that may arise with your API design early in the development phase since it will create problems addressing them when the product is released or just before it releases.  

Usability API design testing goes through hundreds of designs to find which one is the ideal one. It’s your job to ensure that you choose the one that satisfies your customers out of all these designs!

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