What are the essential steps for documenting a web API?

1 Define your audience

Before you start writing, you need to know who your target audience is and what they need from your documentation. Are they developers who want to integrate your API into their applications? Are they end-users who want to understand how your API works and what it offers? Are they testers who want to verify your API's performance and reliability? Depending on your audience, you may need to adjust your tone, level of detail, and format of your documentation.

2 Choose a format and tool

There are many formats and tools available for documenting a web API, such as RESTful API Modeling Language (RAML), OpenAPI Specification (OAS), Swagger, API Blueprint, and Postman. Each format and tool has its own advantages and disadvantages, such as readability, compatibility, interactivity, and automation. You should choose a format and tool that suits your API's style, features, and requirements, as well as your audience's preferences and expectations.

3 Write an overview

An overview is a brief introduction to your web API that summarizes its purpose, scope, and main features. It should answer questions such as: What does your API do? What problems does it solve? What are the benefits of using it? How does it relate to other APIs or services? An overview should also provide some basic information about your API's architecture, protocols, authentication, and versioning.

4 Document your endpoints

Your endpoints are the core of your web API, as they define the interactions between your API and its clients. For each endpoint, you should document its URL, HTTP method, parameters, headers, body, response status codes, and response body. You should also provide examples of request and response messages, as well as explanations of the logic, errors, and validations behind each endpoint. You can use code blocks, tables, diagrams, or other visual aids to illustrate your endpoints clearly and consistently.

5 Document your data models

Your data models are the structures and formats of the data that your web API sends and receives. For each data model, you should document its name, description, properties, types, constraints, and relationships. You should also provide examples of how the data model looks like in JSON, XML, or other formats. You can use schemas, definitions, or other standards to describe your data models accurately and concisely.

7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?