REST API Design Guidelines

Introduction

What you will find in this repository is a list of guidelines we follow at Inaka when designing our REST APIs. These guidelines are not taxative, some exceptions can be found here or there, but we do base our tools (like Jayme, Dayron and SumoREST) on them. That's why, if you're going to use one of those tools, it would be much simpler to have a server that complies to the following guides.

Contact Us

And you can check all of our open-source projects at inaka.github.io

Conventions & Rules

Maintain existing style

When editing a system written by someone else, stick to the style in which it was designed. If a project has an overall style, stick to that when adding, removing or updating API endpoints as well.

Examples

Good

• POST /set_table
• GET /get_table/x
• POST /set_chair ⃪ added by you

Bad

• POST /set_table
• GET /get_table/x
• POST /chairs ⃪ added by you

Ugly

• POST /set_table
• GET /tables/x
• POST /api/v2.3/set_chair ⃪ added by you

Reasoning

It's better to maintain a system that just looks ugly to you than to have a system that looks half ugly to you, half ugly to somebody else.

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Use snake_case with JSON

When the endpoint returns or receive a JSON, the keys should always be in snake_case.

Examples

Good

{
	"caption": "string",
	"comment_count": 0,
	"created_at": "2017-03-07T18:57:44.622Z",
	"id": "string",
	"like_count": 0,
	"media_type": "image",
	"owner": "string"
}

Bad

{
	"caption": "string",
	"commentCount": 0,
	"createdAt": "2017-03-07T18:57:44.622Z",
	"id": "string",
	"likeCount": 0,
	"mediaType": "image",
	"owner": "string"  
}

Reasoning

Even though in some programming languages is common to name variables or object instances with camelCase names, we consider the snake_case is the most readable and understandable way to name the key fields on a JSON object.

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Don't use response envelopes by default

When the endpoint returns, for example, an array, it should be returned as a plain array, not a dictionary with the array as a value.

Examples

Good

[
	{
		"like_count": 0,
		"id": "string",
		"media_type": "comment",
		"owner": "string"
	},
	{
		"like_count": 0,
		"id": "string",
		"media_type": "comment",
		"owner": "string"
	},
	{
		"like_count": 0,
		"id": "string",
		"media_type": "comment",
		"owner": "string"
	}
]

Bad

{ "items" :
	[
		{
			"like_count": 0,
			"id": "string",
			"media_type": "comment",
			"owner": "string"
		},
		{
			"like_count": 0,
			"id": "string",
			"media_type": "comment",
			"owner": "string"
		},
		{
			"like_count": 0,
			"id": "string",
			"media_type": "comment",
			"owner": "string"
		}
	]
}

Reasoning

If you're calling a GET on /entities , you're asking for a list of entities, not an object with the entities inside one of its properties. So don't envelope things that should be retrieved directly.

---

Use all HTTP verbs (Not everything is a GET)

Use all the HTTP verbs. If you have to Create something use POST. If you want to Read something use GET. If you want to Update something use PATCH or PUT. If you want to Delete something use DELETE. Always remember C.R.U.D. (Create, Read, Update, Delete) when setting the verb for your endpoint.

Examples

Good

Creating a comment on a media item:

• POST /media/:media_id/comments This Creates a comment related to the media id you pass along in the URL.

Reading comments on a media item:

• GET /media/:media_id/comments This Reads all the comments related to the media id you pass along in the URL.

Updating ( editing ) the comment content on a media item:

• PUT /media/:media_id/comments/:id This Updates all the fields of the comment with the id you pass along in the URL

Deleting a comment on a media item:

• DELETE /media/:media_id/comments/:id This Deletes the comment with the id you pass along in the URL

Bad

Creating a comment on a media item:

• GET /media/:media_id/create_comment?text=comment%20text

Updating the comment content on a media item:

• GET /media/:media_id/update_comment?text=comment%20new%20text

Deleting a comment on a media item:

• GET /media/:media_id/delete_comment?id=:id

Reasoning

Using the right HTTP Verb on each endpoint will make clearer what the endpoint is made for and what we should expect it to do, receive and return.

---

Use Nouns for endpoints names (URLs)

Your endpoint names should be always nouns, not verbs.

Examples

Good

Getting a user

• GET /users/:id The endpoint retrieves the user with the id you pass along in the url.

Creating a user

• POST /users This creates a user with the info you pass along in the request body.

Deleting a user

• DELETE /users/:id This deletes the user with the id you pass along in the url.

Bad

Getting a post

• GET /get/posts?id=:id This is wrong because you already established that it is a GET. Using /get on the endpoint name is redundant

Creating a post

• POST /create/post Same as above, you already estabished that you're going to create something with the POST so, again, the create is redundant.

Deleting a post

• POST /delete_post/:id

  In this case you're using POST (a verb that's intended to be used for creation) to delete an object. That's semantically wrong. You should use DELETE for that, instead. If you do so, you'll notice that you no longer need to add delete to your url and that then your url will clearly identify the object being deleted.

Reasoning

Your endpoints should reflect what they do based on the HTTP Verb plus the endpoint name (noun). Therefore it makes sense that doing a GET to /entities retrieves a list of entities. On the contrary, doing a GET to /get/entity looks redundant and it's not self descriptive. Let's try with another example: POST /update_entity/:id. That, semantically speaking, should be interpreted as creating/adding an entity to the update_entity set. If your intention was to update the entity with id :id, you should've used PUT or PATCH /entities/:id instead.

---

Plural nouns or singular nouns?

If your endpoint manages a list or a group of entities instead of just one then it should be named with a plural noun. If it always manages a single entity then it should be named with a singular noun.

Examples

Good

Getting comments from a post

• GET /posts/:id/comments The endpoint retrieves a list of comments for the post with the id you pass along in the url.

Getting the likes count of a post

• GET /posts/:id/like_count The endpoint retrieves the likes count of a post with the id you pass along in the url.

Deleting all the comments from a post

• DELETE /posts/:id/comments The endpoint deletes all the comments from the post with the id you pass along in the url.

Bad

Getting a post

• GET /post/:id You're getting a post from a list/group of posts, so it should be plural /posts/:id.

Updating a post

• PUT /posts You're trying to update a post but you're not passing the id on the url. Passing it along in the request body is wrong.

Deleting a comment from a post

• DELETE /posts/:post_id/comment/:id Here you have a list/group of comments so it should be plural /posts/:post_id/comments/:id. Notice how I changed comment for comments.

Reasoning

Your endpoint name should be clear about the fact that it affects a single object or a group/list of objects. If you do a POST to /posts , you'll find the object you created by doing a GET to /posts/:id.

---

Query String VS. Request Body. Where to send the object?

There are four places where you can add paremeters in your HTTP request: query string, path, body and headers. Query Strings are only valid on GET requests and every parameter they include is or should be used as a filter on the data returned. The only scenario where a parameter goes in the path is to identify a resource. Every other paremeter (in POST, PUT, PATCH, etc) should go in the request body. Any parameter that doesn't match any of the previous rules should go in headers (authentication, API versioning, etc).

Examples

Good

Getting posts for an specific user

• GET /posts?user_id=:id The endpoint retrieves a list of posts whose owner is the user with the id in the url

Rating a post

• PATCH /posts/:id {"rate": 4.5} The endpoint gives the post a rating value.

Geting places nearby the user

• GET /places?latitde=35.002&longitude=55.032 The endpoint retrieves all the places nearby the user's location. Radius is a fixed value on the server.

Bad

Creating a place

• POST /places?latitde=35.002&longitude=55.032&name=awesome%20place&type=restaurant Sending the parameters as a query string on a POST request is wrong. They should be in the request body. Something like

{
	"latitude": 35.002
	"longitude": 55.032
	"name": "awesome place"
	"type": "restaurant"
}

Updating a place

• PATCH /places?id=123&name=incredible%20place Don't send the parameters on the query string unless it is a GET. You should be sending them in the request body like

{
	"id": "123"
	"name": "incredible place"
}

Geting places from Buenos Aires

• GET /places

{
	"city": "Buenos Aires"
}

Don't send the search parameters on the request body if you're using a GET. Your url should be /places?city=Buenos%20Aires

Reasoning

Is a good semantic practice to use query strings only when you're using GET and use the request body to send all the data needed by the endpoint when using POST, PUT, PATCH, etc.

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