A REST API is a contract between your server and every client that uses it. Breaking changes are expensive. Good design from the start pays dividends for years.

Use nouns, not verbs

Resources are nouns. HTTP methods are the verbs.

# bad
GET /getUsers
POST /createUser
DELETE /deleteUser?id=5

# good
GET    /users
POST   /users
DELETE /users/5

HTTP status codes — use them correctly

Version your API

/api/v1/users
/api/v2/users

Versioning lets you evolve the API without breaking existing clients.

Consistent error responses

{
    "error": "validation_failed",
    "message": "Email is required",
    "field": "email"
}

Every error should have the same shape. Clients should never have to guess.

Pagination

GET /posts?page=2&per_page=20

Never return unbounded lists. Always paginate.