Error response format in Rest API - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an error response format in REST APIs?

It is a standard way to send error details from the server to the client, usually in JSON, so the client understands what went wrong.

beginner

Why should error responses include a status code?

Status codes tell the client the type of error (like 404 for not found or 500 for server error) so it can handle the problem properly.

beginner

Name three common fields in a REST API error response.

Common fields are:
1. status - HTTP status code
2. error - short error name
3. message - human-readable explanation

intermediate

What is the benefit of including an error code in the response body?

An error code helps the client identify the exact problem programmatically, beyond just the HTTP status code.

beginner

How can error response formats improve user experience?

Clear error messages help users understand what went wrong and how to fix it, reducing frustration and support requests.

Which HTTP status code usually means 'Resource Not Found'?

A 200

B 404

C 500

D 301

404 means the requested resource was not found on the server.

What field in an error response typically contains a human-readable explanation?

A message

B error_code

C status

D timestamp

The 'message' field explains the error in simple words.

Why include both HTTP status code and error code in a response?

A To provide both general and specific error info

B To increase response size

C Because HTTP requires it

D To confuse the client

HTTP status gives general error type; error code gives specific details.

Which of these is NOT a good practice for error responses?

A Provide error codes for programmatic handling

B Use standard HTTP status codes

C Include clear error messages

D Return empty body on error

Returning an empty body on error makes it hard for clients to understand the problem.

What is a common format for REST API error responses?

A XML

B CSV

C JSON

D Plain text

JSON is the most common and easy-to-use format for REST API error responses.

Describe the key components of a good REST API error response format.

Think about what helps both humans and programs understand the error.

Explain why consistent error response formats are important in REST APIs.

Consider how clients and developers benefit from consistency.

Practice

1. What is the main purpose of an error response format in a REST API?

easy

A. To speed up the API response time

B. To clearly communicate what went wrong during a request

C. To encrypt the data sent to the client

D. To store user information securely

Solution

1. Step 1: Understand the role of error responses

   Error responses tell the client what problem happened when processing their request.

2. Step 2: Identify the main goal

   The main goal is to communicate the error clearly so the client can handle it properly.

3. Final Answer:

   To clearly communicate what went wrong during a request -> Option B

4. Quick Check:

   Error response purpose = clear communication [OK]

Hint: Error responses explain problems clearly to clients [OK]

Common Mistakes:

• Thinking error responses speed up API
• Confusing error format with encryption
• Assuming error responses store data

2. Which of the following is a correct JSON structure for a simple error response in a REST API?

easy

A. {"error": {"code": 404, "message": "Not Found"}}

B. {"status": 200, "message": "Success"}

C. {"data": {"id": 1, "name": "Item"}}

D. {"error_code": "404", "error_msg": "Not Found"}

Solution

1. Step 1: Identify standard error response keys

   Common keys include "error", "code", and "message" to describe the problem.

2. Step 2: Check each option

   {"error": {"code": 404, "message": "Not Found"}} uses "error" with "code" and "message" correctly in JSON format.

3. Final Answer:

   {"error": {"code": 404, "message": "Not Found"}} -> Option A

4. Quick Check:

   Standard error keys = code and message [OK]

Hint: Look for 'error', 'code', and 'message' keys in JSON [OK]

Common Mistakes:

• Confusing success response with error
• Using wrong key names like error_code
• Missing nested error object

3. Given this error response JSON:

{"error": {"code": 401, "message": "Unauthorized"}}

What HTTP status code should the API return?

medium

A. 401

B. 500

C. 404

D. 200

Solution

1. Step 1: Match error code to HTTP status

   The error code 401 means "Unauthorized", which is an HTTP status code for authentication failure.

2. Step 2: Confirm correct HTTP status

   The API should return HTTP status 401 to match the error code in the response body.

3. Final Answer:

   401 -> Option A

4. Quick Check:

   Error code 401 = HTTP status 401 [OK]

Hint: Match error code with HTTP status code [OK]

Common Mistakes:

• Returning 200 for error responses
• Confusing 401 with 404
• Using 500 for client errors

4. You receive this error response from an API:

{"error": {"code": "403", "message": "Forbidden"}}

But your client expects the code as an integer. What is the best fix?

medium

A. Change the message to "Access Denied"

B. Remove the code field entirely

C. Change the code value to an integer 403 in the response

D. Wrap the code in quotes to make it a string

Solution

1. Step 1: Identify data type mismatch

   The code is a string "403" but the client expects an integer 403.

2. Step 2: Fix the data type in the response

   Change the code value from a string to an integer to match client expectations.

3. Final Answer:

   Change the code value to an integer 403 in the response -> Option C

4. Quick Check:

   Match data types for code field [OK]

Hint: Ensure error code data type matches client expectation [OK]

Common Mistakes:

• Removing important error fields
• Changing message instead of code type
• Leaving code as string when integer needed

5. You want to design an error response format that includes an error code, a message, and optional details for debugging. Which JSON structure below best fits this need?

hard

A. {"error": "Bad Request", "code": 400}

B. {"status": "error", "code": 400, "msg": "Bad Request"}

C. {"error_code": 400, "error_message": "Bad Request"}

D. {"error": {"code": 400, "message": "Bad Request", "details": "Missing 'id' parameter"}}

Solution

1. Step 1: Check required fields in each option

   We need code, message, and optional details inside a clear error object.

2. Step 2: Evaluate each JSON structure

   {"error": {"code": 400, "message": "Bad Request", "details": "Missing 'id' parameter"}} includes all three: code, message, and details nested inside "error".

3. Final Answer:

   {"error": {"code": 400, "message": "Bad Request", "details": "Missing 'id' parameter"}} -> Option D

4. Quick Check:

   Include code, message, and details in error object [OK]

Hint: Include optional details inside error object for clarity [OK]

Common Mistakes:

• Omitting details field
• Using inconsistent key names
• Not nesting error info properly