How can you write API documentation for a complex system?

Defining the scope and audience is crucial for API documentation as it ensures the information is relevant and accessible. For complex systems, it's important to balance technical details with readability to cater to both developers and less technical stakeholders. Structuring documentation with clear headings and a logical flow aids in navigability, while regular updates ensure the content reflects the latest version of the API. Including real-world use cases can also bridge the gap between abstract concepts and practical application.

Scope: Understand the entire API system and its functionalities. Document what the API does, what it doesn't do, its limitations, and its intended use cases. Audience: Identify who will be using the API documentation. This could include developers, testers, product managers, or other stakeholders. Tailor the documentation style and depth accordingly.

One thing that i really found helpful was that - whenever there is a complex change in the api(like entity change or structure of entity change), its better to go with "API deprecation" rather than modifying the existing API... this will ensure that the existing apis are running( in case there is discrepancy of information between ui and backend team) and then slowly remove them in the future versions...

Consistency is key in documentation. Adopting a standard format like OpenAPI ensures that users can easily navigate through different sections such as endpoints, parameters, and responses. Additionally, maintaining a consistent writing style helps in readability and comprehension. Clear headings, bullet points, and tables can organize information effectively. I'd also include a glossary for technical terms to assist users in understanding the terminology.

Consistent Structure: Maintain a consistent structure throughout the documentation. This helps users navigate and find information easily. Standard Conventions: Follow industry-standard conventions. For RESTful APIs, this often includes documenting endpoints, request methods, request/response formats, authentication methods, etc. Clear Language: Use clear and simple language. Avoid jargon when possible, and explain technical terms.

Each endpoint should be thoroughly documented, including its purpose, URL structure, supported HTTP methods, and expected responses. Parameters should be clearly defined, specifying their data types, allowed values, and any validation rules. It's also important to mention any authentication requirements and rate limiting policies. Providing practical examples of API calls using tools like cURL or Postman can aid developers in understanding how to interact with the endpoints.

Endpoint List: Provide a list of all endpoints along with their descriptions. Organize them logically, such as grouping by resource type. Endpoint Details: URL: Include the full URL for each endpoint. HTTP Method: Specify the HTTP method (GET, POST, PUT, DELETE, etc.). Description: Explain what the endpoint does and its purpose. Parameters: List all parameters (query parameters, path parameters, request body parameters) with descriptions, types, and whether they are required or optional. Response: Describe the possible responses, including status codes and response body structures.

Examples are essential for demonstrating how to use the API effectively. I would add real-world examples and code snippets that show how to make requests and handle answers. These examples should include both successful and unsuccessful cases to help developers prepare for various possibilities. In addition, I'd provide advice on error handling and best practices for ensuring strong integration with the API. Interactive documentation tools, such as Swagger UI, can improve the user experience by enabling developers to test endpoints straight from the documentation.

Request Examples: Provide sample requests for each endpoint, including headers, parameters, and request bodies. Use common scenarios that cover different use cases. Response Examples: Show example responses for each endpoint, including success and error responses. Include sample JSON or XML structures. Code Snippets: Offer code snippets in various programming languages (such as cURL, Python, JavaScript) to demonstrate how to make requests to the API. Include code for handling responses and error cases.