What is the golden rule of API design?

The golden rule of API design is to treat the API as a product. This means designing the API with the end-user (developers) in mind, ensuring that it is simple, consistent, reliable, and intuitive. Just like any product, the API should aim to provide a great user experience for developers by being easy to understand, use, and maintain.

Key Principles of the Golden Rule:

1. Simplicity: Keep the API simple and intuitive. A well-designed API should have clear, predictable behavior with minimal complexity, making it easy for developers to interact with the API without confusion.

2. Consistency: Ensure that the API follows consistent conventions in naming, input/output formats, and error handling. This makes it easier for developers to predict and understand how the API works without frequent reference to the documentation.

3. Documentation: Provide thorough and clear documentation. APIs are only as good as the documentation that explains how to use them. Clear instructions, examples, and error codes help developers implement the API smoothly.

4. Versioning: The API should maintain backward compatibility when changes or updates are made, ensuring that previous users don't face interruptions or issues with their applications.

5. Security: APIs should implement strong security measures like authentication, rate-limiting, and encryption to protect data and ensure safe interactions.

By treating the API as a product and focusing on the experience for its end users, API designers can create more efficient, developer-friendly interfaces that lead to greater adoption and ease of use.

Sources:

1. Cloud Elements: API Design Principles
2. RedHat: Key API Design Principles