Why APIs Are Only as Good as Their Documentation – 6 Tips to Get it Right

In today’s digitalized world, APIs (Application Programming Interface) are indispensable,
also for financial service providers who want to remain competitive. Due to digitalization and automation of work processes leads to data being exchanged via applications, and this is where APIs come into play. They are thus a key aspect of a company’s success, which
can also be proven by impressive figures:

• According to Akamai, API calls account for around 83% of all internet traffic (as of 2019).
• According to Cloudflare, the banking sector in particular has great potential with annual API traffic growth of over 70% (as of 2021).
• Postman reports that almost 90% of the companies surveyed would like to invest the same or even more time in the development of APIs in the future (as of 2022).

But all these advances in performance, reliability and scalability are of little use to API users if they are not cleanly documented. In our article we explain why API documentation is critical and how 6 essential tips can help you unlock the full potential of APIs.
API users if these are not properly documented. In our article we explain why API documentation is critical and how 6 essential tips can help you unlock the full potential of APIs.
6 essential tips to unleash the full potential of APIs.

What makes for good documentation?

The importance of well-designed API documentation becomes particularly obvious the longer a project lasts and the more smoothly new software is ought to be integrated into the existing architecture. In such cases, API requirements increase significantly. Inadequate documentation can lead to a patchwork of confusingly structured endpoints that complicates development as well as maintenance and jeopardizes the overall success of the project.

To avoid such problems and enable smooth collaboration between different development teams, developers should follow these important points when documenting interfaces:

1. Know the Target Audience

Before writing documentation, it is critical to consider the target audience.
Before writing documentation, it is critical to consider the target audience. For internal development teams, some prior knowledge can be preconditioned, while external users and partners need a detailed explanation of all parameters. In addition, a distinction should be made between Business Analysts and developers. Business Analysts need a comprehensive overview of the functions, while developers expect detailed documentation in order to use the API effectively.

2. Comprehensible and Clearly Structured

Well-structured and understandable documentation is of high importance.
The principle “as much as necessary, but as little as possible” should be applied.

The documentation should start with a short introduction explaining the purpose of the API, the conditions, the available options and the limitations. This way, developers and business analysts can quickly assess whether the API covers their requirements.

Afterwards the servers, their application and the available authentication methods are shown. The main part includes the endpoints with methods, paths, parameters, body and response status codes. Each parameter should contain type, description and mandatory status. To facilitate orientation, a glossary of terms used can optionally be added.

3. Don’t Reinvent the Wheel

Well-known frameworks are based on markup languages such as YAML, JSON, or XML, which are readable by both machines and humans. Using them offers numerous advantages to both developers and users: Automatic generation of documentation from source code, collaborative work, version management, direct testing of endpoints, and generally saving time by interacting with known structures. There are plenty of options of documentation tools. However, the best choice depends on the use case. Often, the formats can also be converted between each other, so that the advantages of different tools can be combined.

4. Always Keep Up-to-Date and Clearly Highlight Changes in the Release Notes

Nothing is more off-putting to potential users than incomplete or incorrect documentation. Therefore, it is essential to update the documentation regularly after the initial release. To make it clear at a glance what has changed, the modified passages should also be noted in the release notes.

5. Theory Is Good, Examples Are Better

No documentation should skimp on examples. Especially for inexperienced or new users, they represent the optimal starting point for trying out a particular function of an API without having to have much prior knowledge. Often, the examples also serve as a basis for building more complex queries. Therefore, at least one example should be added for each endpoint to give users a better understanding and facilitate practical use.

6. Document not Only the Requests, but Also the Responses

A complete API documentation should not only contain detailed information about the requests, but also provide information about the responses. Responses are of central importance in communication between programs, since they contain the retrieved data.

Error handling in the responses is also particularly important. In the event of a failed query, it should be clearly described which status code indicates which cause. This allows API users to efficiently identify and resolve errors.

Conclusion

The art of documentation is an often neglected discipline in interface development. What may sound like extra work at first glance ultimately saves both developers and users of an interface a lot of time. Good documentation promotes collaboration and smooth exchange between all parties involved. In summary, high-quality API documentation is crucial to the success of an interface.