當成功或失敗都必須要讓人知道，有以下兩個部分

1. HTTP status codes
2. Custom error codes and messages

書中範例

Code	Text	Description
161	你不能追隨這個使用者	403 status code
179	你沒有授權去看這個	403 status code

JSON-API

是一個標準主要是針對 requests 和 responses 的格式

錯誤格式可能有以下屬性

• id
• href
• status
• code
• title
• detail
• links
• path

2XX success

• 200 - 通用 - Generic everything is OK
• 201 - 建立資源 - Created something OK
• 202 - 接受請求但非同步執行 - Accepted but is being processed async

3XX redirection

4XX client errors

• 400 - 通用 -Bad Request (should really be for invalid syntax, but some folks use for validation)
• 401 - 沒授權 - Unauthorized (no current user and there should be)
• 403 - 禁止 -The current user is forbidden from accessing this data
• 404 - 不正確的route- That URL is not a valid route, or the item resource does not exist
• 405 - Method Not Allowed (your framework will probably do this for you)
• 410 - 資料已經刪除 - Data has been deleted, deactivated, suspended, etc.

5XX service errors

• 500 - Something unexpected happened, and it is the APIs fault
• 503 - API is not here right now, please try again later