API design is an essential topic for teams looking to perfect their API strategy. A well-designed API brings numerous benefits, such as improved developer experience, faster documentation, and higher adoption rates.

But what exactly constitutes good API design?

In this post, I'll walk you through several best practices for designing APIs.

Characteristics of a Well-Designed API

An effective API design should have the following characteristics:

Easy to Read and Work With

A well-designed API will be intuitive and easy to work with. Developers who frequently interact with the API should be able to quickly memorize its resources and the operations associated with them.

Hard to Misuse

A well-structured API minimizes the chances of misuse. It ensures smooth implementation and integration, while also providing informative feedback to help developers avoid mistakes.

Complete and Concise

A complete API allows developers to build fully functional applications with the data your API exposes. While completeness is a gradual process, a good API should be capable of supporting the developer's needs as it grows and evolves.

For illustration, let's take the example of a task management app. The app lets users create tasks, assign them to team members, set deadlines, and categorize them by project.

Collections, Resources, and Their URLs

Understanding Resources and Collections

Resources are the key entities in a RESTful API. A resource represents an object that’s important enough to be referenced on its own. Resources have data, relationships to other resources, and methods that allow developers to interact with them. A group of resources is called a collection. The contents of collections and resources will vary based on your organizational needs.

In the context of our task management app, you might have resources such as users, tasks, and projects. These could be accessed through collections and resources via specific URLs:

• /users: a collection of all users

• /users/John: a resource for a specific user

• /tasks: a collection of tasks

• /tasks/123: a resource for a specific task

Describe URLs Better With Nouns

URLs should be simple and intuitive. Long, complicated URLs can be error-prone, making them harder to work with. A good practice is to use plural nouns for collections and make sure that the resource names are self-explanatory. For example, in the task management app, /users and /tasks are clear and easy to understand.

Describe Resource Functionality with HTTP Methods

RESTful APIs rely heavily on HTTP methods to define operations on resources. Here’s a quick rundown of the standard HTTP methods for CRUD operations:

Method	Description
GET	Retrieve a resource
POST	Create a new resource
PUT	Update an existing resource
PATCH	Update parts of an existing resource
DELETE	Delete a resource

It’s important to avoid using verbs in the URL since the HTTP methods already define the action. For example, you might use /tasks with the GET method to retrieve tasks and /tasks/123 with the DELETE method to remove a specific task.

Responses

Provide Helpful Feedback to Developers

Providing clear, informative feedback helps developers succeed and improves adoption. When a request is made, the server's response should offer useful information. For example:

• If the client makes an erroneous request, return a 400-type error (client error) with details on how to fix the issue.

• If there’s an issue on the server side, return a 500-type error (server error).

• A successful request should result in a 200-type response.

Be sure to document your errors clearly, helping developers understand what went wrong and how they can correct it.

Give Examples for All Your GET Responses

Every GET response should include a simple example of what developers can expect. Here’s an example for the /users collection in the task management app:

{

"data": [

{

"username": "johnDoe",

"email": "john@example.com",

"joined_date": "2022-06-15T10:00:00+0000"

},

{

"username": "janeSmith",

"email": "jane@example.com",

"joined_date": "2023-03-20T15:30:00+0000"

}

]

}

Including example responses like this allows developers to quickly understand what to expect, improving their experience and making integration easier.

Requests

Handle Complexity Elegantly

APIs often need to expose a variety of data and relationships between resources. However, too many resources can overcomplicate things. Rather than creating separate resources for every possible relationship, use parameters to keep things simple and efficient.

Get Started with API Design

There's no one-size-fits-all approach to API design. The guidelines above offer advice on creating APIs that are intuitive and easy to integrate with, but it’s important to adapt them based on your use case and the needs of your developers. A great API is one that empowers developers to build creative applications with ease, and the design decisions you make should always focus on enhancing that experience.