Problem Details (RFC 7807) format in Rest API

Introduction

This format helps APIs explain errors clearly and consistently. It makes it easier for clients to understand what went wrong.

When your API needs to send error information to clients.

When you want to standardize error messages across different parts of your API.

When you want clients to handle errors in a predictable way.

When debugging problems between client and server.

When you want to provide helpful links or details about errors.

Syntax

Rest API

{
  "type": "string (URI)",
  "title": "string",
  "status": "integer (HTTP status code)",
  "detail": "string",
  "instance": "string (URI)",
  "additional_fields": "optional extra info"
}

type is a URI that identifies the error type. It should be a URL but does not have to be reachable.

title is a short, human-readable summary of the problem.

Examples

This example shows a user error about insufficient credit with details and a link to the specific request.

Rest API

{
  "type": "https://example.com/probs/out-of-credit",
  "title": "You do not have enough credit.",
  "status": 403,
  "detail": "Your current balance is 30, but that costs 50.",
  "instance": "/account/12345/transactions/abc"
}

This example explains a validation error for a user input field.

Rest API

{
  "type": "https://example.com/probs/invalid-input",
  "title": "Invalid input.",
  "status": 400,
  "detail": "The 'email' field must be a valid email address.",
  "instance": "/users/5678"
}

Sample Program

This Flask app returns a Problem Details JSON response with HTTP status 403 and the correct content type when you visit /error.

Rest API

from flask import Flask, jsonify

app = Flask(__name__)

@app.route('/error')
def error():
    problem = {
        "type": "https://example.com/probs/out-of-credit",
        "title": "You do not have enough credit.",
        "status": 403,
        "detail": "Your current balance is 30, but that costs 50.",
        "instance": "/account/12345/transactions/abc"
    }
    response = jsonify(problem)
    response.status_code = problem["status"]
    response.headers["Content-Type"] = "application/problem+json"
    return response

if __name__ == '__main__':
    app.run(debug=True)

Important Notes

Always set the HTTP status code to match the status field in the problem details.

Use the Content-Type header value application/problem+json to indicate this format.

You can add extra fields if needed, but keep the standard fields for compatibility.

Summary

Problem Details format standardizes error responses in APIs.

It uses a JSON object with fields like type, title, status, detail, and instance.

This helps clients understand and handle errors better.

Practice

1. What is the main purpose of the Problem Details (RFC 7807) format in REST APIs?

easy

A. To speed up API response times

B. To standardize error responses so clients can understand errors better

C. To encrypt API responses for security

D. To format successful data responses uniformly

Solution

1. Step 1: Understand the role of Problem Details format

   The format is designed to provide a consistent way to report errors in APIs.

2. Step 2: Identify the main benefit

   It helps clients understand and handle errors better by standardizing error responses.

3. Final Answer:

   To standardize error responses so clients can understand errors better -> Option B

4. Quick Check:

   Purpose = Standardize error responses [OK]

Hint: Remember: Problem Details = standardized error info [OK]

Common Mistakes:

• Confusing error format with data encryption
• Thinking it speeds up API responses
• Assuming it formats successful responses

2. Which of the following is a REQUIRED field in the Problem Details JSON object according to RFC 7807?

easy

A. type

B. status

C. detail

D. instance

Solution

1. Step 1: Recall required fields in RFC 7807

   The RFC requires the "type" field to identify the error type URI.

2. Step 2: Check other fields

   Fields like "status", "detail", and "instance" are optional but recommended.

3. Final Answer:

   type -> Option A

4. Quick Check:

   Required field = type [OK]

Hint: Only 'type' is mandatory in Problem Details [OK]

Common Mistakes:

• Assuming 'status' is required
• Confusing 'detail' as mandatory
• Thinking 'instance' is always needed

3. Given this Problem Details JSON response:

{"type": "https://example.com/probs/out-of-credit", "title": "You do not have enough credit.", "status": 403, "detail": "Your current balance is 30, but that costs 50.", "instance": "/account/12345/msgs/abc"}

What is the HTTP status code indicated?

medium

A. 403

B. 404

C. 200

D. 500

Solution

1. Step 1: Locate the status field in JSON

   The JSON has "status": 403, which indicates the HTTP status code.

2. Step 2: Understand the meaning of 403

   403 means Forbidden, matching the error about insufficient credit.

3. Final Answer:

   403 -> Option A

4. Quick Check:

   Status code = 403 [OK]

Hint: Look for 'status' field for HTTP code [OK]

Common Mistakes:

• Confusing status with 'detail' content
• Picking 200 as success code
• Ignoring the numeric status field

4. You receive this Problem Details JSON:

{"title": "Invalid input", "status": 400, "detail": "Missing required field 'name'"}

What is missing that violates RFC 7807 requirements?

medium

A. The 'title' field should be a URL

B. The 'status' field should be a string

C. The 'detail' field should be omitted

D. The 'type' field is missing

Solution

1. Step 1: Check required fields in the JSON

   The 'type' field is required by RFC 7807 but is missing here.

2. Step 2: Validate other fields

   'status' is correctly a number, 'detail' and 'title' are valid types.

3. Final Answer:

   The 'type' field is missing -> Option D

4. Quick Check:

   Missing required field = type [OK]

Hint: Always include 'type' field in Problem Details [OK]

Common Mistakes:

• Thinking 'status' must be string
• Removing 'detail' field
• Assuming 'title' must be URL

5. You want to create a Problem Details response for a rate limit error. Which JSON object correctly follows RFC 7807 and clearly informs the client about the error?

hard

A. {"type": "rate-limit", "title": "Error", "status": 429, "detail": "Limit reached"}

B. {"title": "Rate limit exceeded", "status": "429", "detail": "Too many requests", "instance": "/api/v1/resource"}

C. {"type": "https://example.com/probs/rate-limit", "title": "Rate limit exceeded", "status": 429, "detail": "You have sent too many requests in a short time.", "instance": "/api/v1/resource"}

D. {"type": "https://example.com/probs/rate-limit", "title": "Rate limit exceeded", "status": 200, "detail": "Too many requests"}

Solution

1. Step 1: Check required fields and correct types

   {"type": "https://example.com/probs/rate-limit", "title": "Rate limit exceeded", "status": 429, "detail": "You have sent too many requests in a short time.", "instance": "/api/v1/resource"} includes 'type' as a URI, 'title', numeric 'status' 429, 'detail', and 'instance' fields correctly.

2. Step 2: Validate status code and clarity

   Status 429 means Too Many Requests, matching the error. Other options have missing or wrong fields or wrong status codes.

3. Final Answer:

   {"type": "https://example.com/probs/rate-limit", "title": "Rate limit exceeded", "status": 429, "detail": "You have sent too many requests in a short time.", "instance": "/api/v1/resource"} -> Option C

4. Quick Check:

   Correct fields and status = {"type": "https://example.com/probs/rate-limit", "title": "Rate limit exceeded", "status": 429, "detail": "You have sent too many requests in a short time.", "instance": "/api/v1/resource"} [OK]

Hint: Use URI in 'type' and correct numeric 'status' [OK]

Common Mistakes:

• Using string instead of number for status
• Missing 'type' or using non-URI string
• Wrong HTTP status code for error