How to write a great API specification

Understand your audience

The first step in writing a great API specification is to understand your audience. Who will be using your API? What are their technical backgrounds and expertise levels? What are their specific needs and use cases? By understanding your audience, you can tailor your specification to their needs and provide them with the information they need to use your API effectively.

Use clear and concise language

When writing an API specification, it’s important to use clear and concise language that is easy to understand. Avoid technical jargon and acronyms that may be unfamiliar to your audience, and use plain language to explain complex concepts. Use diagrams, tables, and examples to illustrate your points and make your specification more accessible.

Define message formats and fields

The heart of an API specification is the message formats and fields that define the content of the messages exchanged between trading systems. It’s important to define these clearly and consistently, using a consistent syntax and structure. Use descriptive field names that clearly indicate the content of the field, and define any abbreviations or codes that are used in the specification.

In the world of FIX, there is often a lot of assumed knowledge about the purpose of fields, messages or values. Having a well-understood, industry-wide dictionary such as the FIX protocol can be a great time-saver, but don’t forget that your reader may have connected to hundreds of FIX APIs before, or this could be their first one – don’t assume too great knowledge.

Provide examples

Providing examples is one of the most effective ways to help your audience understand the content of your API specification. Use real-world examples that illustrate how the API is used in practice, and provide examples of message formats and fields to help your audience understand how to construct and parse messages.

Include error handling and recovery procedures

Error handling and recovery procedures are critical components of any API implementation. Your API specification should define how errors are handled and what recovery procedures should be followed in the event of an error. Include detailed error codes and messages, as well as guidance on how to troubleshoot and resolve errors.

Consider scalability and extensibility

When writing an API specification, it’s important to consider scalability and extensibility. Your specification should be designed to support a wide range of use cases and accommodate future growth and expansion. Consider the potential for future updates and enhancements, and design your specification with flexibility and extensibility in mind.

Provide implementation guidance

Finally, it’s important to provide implementation guidance to help developers and traders implement and use your API API effectively. This might include guidance on how to test the API, how to integrate it with other systems, and best practices for using the API in different trading scenarios.

In conclusion, writing a great API specification requires a combination of technical expertise and effective communication skills. By understanding your audience, using clear and concise language, defining message formats and fields, providing examples, including error handling and recovery procedures, considering scalability and extensibility, and providing implementation guidance, you can create a specification that is easy to use, reliable, and scalable. A great API specification can help your API stand out in a crowded market, attract more users, and drive greater success in the financial markets.

Talk to us today about writing better API specifications for your organisation.