API Design Principles

Designing effective APIs is both an art and a science. This guide outlines the key principles and best practices for designing RESTful APIs with api.vision, helping you create intuitive, scalable, and maintainable interfaces.

Core RESTful Design Principles

RESTful API design follows a set of architectural constraints and principles that help create scalable, maintainable web services. Here are the core principles:

Resource-Based

Design your API around resources (nouns) rather than actions (verbs). A resource is any entity that can be identified, named, addressed, or handled in your system.

Good:

/users, /products, /orders

Avoid:

/getUsers, /createProduct

HTTP Methods for Operations

Use standard HTTP methods (GET, POST, PUT, PATCH, DELETE) to perform operations on resources.

Method	Operation	Example
GET	Read	`GET /users` - List users
POST	Create	`POST /users` - Create user
PUT	Update (replace)	`PUT /users/123` - Replace user
PATCH	Update (partial)	`PATCH /users/123` - Update user fields
DELETE	Delete	`DELETE /users/123` - Delete user

Stateless Communication

Each request from a client to the server must contain all the information needed to understand and process the request. The server should not store client state between requests.

This enables high scalability as the server doesn't need to maintain, update, or communicate client state, allowing requests to be handled by any available server in a cluster.

Uniform Interface

Your API should follow consistent patterns and conventions, making it predictable and easier to use. This includes using standard HTTP methods consistently, returning appropriate status codes, and following naming conventions.

URL Structure Guidelines

A well-designed URL structure is intuitive and clearly communicates the resource hierarchy and relationships:

Use Hierarchical Structure

Example:

/users/{userId}/posts/{postId}/comments

This clearly shows that comments belong to a post, which belongs to a user.

Use Plurals for Collection Resources

Good:

/users, /products, /orders

Avoid:

/user, /product, /order

Use Lowercase Letters and Hyphens

Good:

/user-profiles, /shipping-addresses

Avoid:

/UserProfiles, /shipping_addresses

Use Query Parameters for Filtering, Sorting, and Pagination

Examples:

/products?category=electronics/products?sort=price/products?page=2&limit=10

Response Formats and Headers

Consistent response formats and appropriate headers help make your API more user-friendly:

Use JSON as the Default Format

JSON (JavaScript Object Notation) is the most widely used format for API responses due to its simplicity, readability, and compatibility with many programming languages.

{
  "id": 123,
  "username": "johndoe",
  "email": "john@example.com",
  "createdAt": "2023-04-15T10:30:00Z"
}

Use Consistent Property Naming

Choose a naming convention for response properties and stick to it. In api.vision, we use camelCase for property names.

Good:

firstName, createdAt, orderId

Avoid mixing:

first_name, CreatedAt, OrderID

Include Metadata for Collections

When returning collections, include metadata like total count, pagination info, etc., either in the response or through HTTP headers.

Response Headers Approach:

X-Total-Count: 42X-Page: 2X-Total-Pages: 5

Use Content Negotiation

Support content negotiation through the Accept header to allow clients to specify their preferred response format.

Example Request Header:

Accept: application/json

HTTP Status Codes

Using appropriate HTTP status codes helps clients understand the result of their request without having to parse the response body:

Status Code	Description	Usage Example
200 OK	Request succeeded	Successful GET, PUT, PATCH requests
201 Created	Resource created	Successful POST request that creates a resource
204 No Content	Request succeeded, no content to return	Successful DELETE request
400 Bad Request	Invalid request format or parameters	Missing required fields, invalid format
401 Unauthorized	Authentication required	Missing or invalid authentication credentials
403 Forbidden	Authenticated but not authorized	User doesn't have permission to access the resource
404 Not Found	Resource not found	Requesting a non-existent resource
422 Unprocessable Entity	Request format is valid but content is invalid	Validation errors in the request data
429 Too Many Requests	Rate limit exceeded	Client has sent too many requests in a given time
500 Internal Server Error	Server encountered an error	Unexpected server-side error

Error Handling

Proper error handling helps clients understand what went wrong and how to fix it:

Use Descriptive Error Messages

Error messages should be clear, concise, and actionable, helping the client understand what went wrong.

{
  "status": 400,
  "error": "Bad Request",
  "message": "Email address is required",
  "path": "/users"
}

Include Validation Details

For validation errors, include details about which fields failed validation and why.

{
  "status": 422,
  "error": "Validation Error",
  "message": "Request validation failed",
  "errors": [
    {
      "field": "email",
      "message": "Must be a valid email address"
    },
    {
      "field": "password",
      "message": "Must be at least 8 characters long"
    }
  ]
}

Don't Expose Sensitive Information

Error messages should not include sensitive information like stack traces, internal paths, or database details.

Good:

"message": "Authentication failed"

Avoid:

"message": "DB connection failed: mysql://user:password@..."

API Versioning

API versioning helps you evolve your API without breaking existing clients:

URL Path Versioning

Example:

/v1/users/v2/users

This is the most straightforward approach and is used by api.vision. It makes it clear which version of the API the client is using.

Header-Based Versioning

Example:

Accept: application/vnd.company.v1+json

This approach keeps the URLs clean but requires clients to send the correct headers.

Query Parameter Versioning

Example:

/users?version=1/users?api-version=2.1

This approach is simple but can lead to version parameters being forgotten or mixed with other query parameters.

Security Considerations

Securing your API is critical to protect your data and systems:

Use HTTPS Everywhere

Always use HTTPS to encrypt data in transit, preventing man-in-the-middle attacks and eavesdropping. api.vision automatically secures all endpoints with HTTPS.

Implement Authentication and Authorization

Use appropriate authentication mechanisms (like JWT, OAuth) and implement proper authorization checks to control access to resources.

Validate Input

Always validate user input to prevent injection attacks, XSS, and other security vulnerabilities. api.vision includes built-in validation based on your resource definitions.

Implement Rate Limiting

Protect your API from abuse by implementing rate limiting. Return 429 Too Many Requests status with a Retry-After header when limits are exceeded.

Documentation

Good documentation is essential for API adoption and usage:

Document All Endpoints

Document every endpoint, including URL, HTTP method, request parameters, request body, response format, and possible status codes.

Provide Examples

Include request and response examples for each endpoint to help users understand how to use the API.

Use OpenAPI/Swagger

Consider using OpenAPI (formerly Swagger) to document your API. api.vision can automatically generate OpenAPI documentation based on your resource definitions.

Summary of Best Practices

Here's a quick summary of the key design principles to follow:

Design around resources, not actions
Use HTTP methods appropriately (GET, POST, PUT, PATCH, DELETE)
Keep communication stateless
Use a consistent URL structure with plural nouns for resources
Leverage query parameters for filtering, sorting, and pagination
Return appropriate HTTP status codes
Provide helpful, detailed error messages
Version your API to allow evolution without breaking clients
Implement security best practices
Document your API thoroughly

Tip: api.vision's Auto-Generated APIs

api.vision automatically generates RESTful APIs following these best practices based on your resource definitions. You can focus on defining your resources and relationships, and api.vision will create a well-designed API that follows these principles.