Schema documentation in GraphQL - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is schema documentation in GraphQL?

Schema documentation in GraphQL is the practice of adding descriptions to types, fields, and arguments in the schema to explain their purpose and usage clearly.

beginner

How do you add a description to a GraphQL type or field?

You add a description by placing a string in triple quotes ("""Description""") just before the type or field definition in the schema.

beginner

Why is schema documentation important in GraphQL?

It helps developers understand what each part of the schema does, making it easier to use and maintain the API without confusion.

intermediate

Can you document arguments in GraphQL schema? How?

Yes, you can add descriptions to arguments by placing triple-quoted strings just before the argument definition inside the field.

intermediate

What tools can use GraphQL schema documentation to improve developer experience?

Tools like GraphiQL, Apollo Studio, and GraphQL Playground use schema documentation to show helpful descriptions and hints while exploring the API.

How do you add a description to a GraphQL field?

A Use a special @doc directive

B Add a comment with // before the field

C Place a triple-quoted string before the field definition

D Descriptions are not supported in GraphQL

GraphQL uses triple-quoted strings placed before types or fields to add descriptions.

What is the main benefit of schema documentation in GraphQL?

A Improves API security

B Helps developers understand the API

C Speeds up query execution

D Automatically generates database tables

Schema documentation helps developers understand the API's purpose and usage.

Can you document arguments in a GraphQL schema?

A Yes, by placing triple-quoted strings before the argument

B Yes, but only in comments outside the schema

C No, only types and fields can be documented

D No, arguments are self-explanatory

Arguments can have descriptions by placing triple-quoted strings before them.

Which of these tools uses GraphQL schema documentation to show descriptions?

A GraphiQL

B MySQL Workbench

C Postman

D MongoDB Compass

GraphiQL uses schema documentation to display helpful descriptions.

What syntax is used for descriptions in GraphQL schema?

A JSON objects

B Single-line comments with //

C XML tags <desc></desc>

D Triple-quoted strings """Description"""

GraphQL uses triple-quoted strings for descriptions.

Explain how to add documentation to a GraphQL schema and why it is useful.

Think about how descriptions appear in the schema and how tools use them.

Describe the role of schema documentation in GraphQL developer tools.

Consider how tools like GraphiQL display schema info.

Practice

1. What is the purpose of using triple quotes """ in GraphQL schema documentation?

easy

A. To define a new type in the schema

B. To write comments that are ignored by the server

C. To add descriptions to types and fields

D. To create a mutation operation

Solution

1. Step 1: Understand triple quotes usage in GraphQL

   Triple quotes """ are used to add descriptions to schema elements like types and fields.

2. Step 2: Differentiate from other schema elements

   They are not for defining types, comments, or mutations but for documentation purposes.

3. Final Answer:

   To add descriptions to types and fields -> Option C

4. Quick Check:

   Triple quotes = descriptions [OK]

Hint: Triple quotes always mean description text in GraphQL [OK]

Common Mistakes:

• Confusing triple quotes with comments
• Thinking triple quotes define types
• Using triple quotes for operations

2. Which of the following is the correct way to add a description to a GraphQL field named age?

easy

A. """User age""" age: Int

B. age: Int # User age

C. age: Int """User age"""

D. "User age" age: Int

Solution

1. Step 1: Identify correct syntax for field description

   In GraphQL, descriptions go before the field using triple quotes.

2. Step 2: Check each option

   """User age""" age: Int places """User age""" before age: Int, which is correct syntax.

3. Final Answer:

   """User age""" age: Int -> Option A

4. Quick Check:

   Description before field with triple quotes = correct [OK]

Hint: Put triple-quoted description right before the field [OK]

Common Mistakes:

• Placing description after the field
• Using single quotes instead of triple quotes
• Using comments (#) instead of descriptions

3. Given this schema snippet, what will the description of the name field be?

type Person {
  """Full name of the person"""
  name: String
  age: Int
}

medium

A. Full name of the person

B. Name of the person

C. No description

D. Person's age

Solution

1. Step 1: Locate the description for the name field

   The triple-quoted string """Full name of the person""" is right above name: String.

2. Step 2: Understand it applies as the description

   This means the description for the name field is exactly that string.

3. Final Answer:

   Full name of the person -> Option A

4. Quick Check:

   Description above field = "Full name of the person" [OK]

Hint: Description above field is the field's doc [OK]

Common Mistakes:

• Assuming no description if not inline
• Confusing field name with description
• Mixing descriptions of different fields

4. Identify the error in this schema documentation snippet:

type Query {
  """Fetch user by ID"""
  user(id: ID!): User
  """Fetch all users"""
  users: [User]
  "Fetch version info"
  version: String
}

medium

A. Descriptions must be after the field, not before

B. The description for version uses double quotes instead of triple quotes

C. Descriptions cannot be used on Query type fields

D. The id argument is missing a description

Solution

1. Step 1: Check description syntax for each field

   The first two fields use triple quotes correctly. The version field uses double quotes "Fetch version info", which is invalid.

2. Step 2: Confirm correct usage

   Descriptions must use triple quotes """ to be valid in GraphQL schema.

3. Final Answer:

   The description for version uses double quotes instead of triple quotes -> Option B

4. Quick Check:

   Descriptions need triple quotes, not double [OK]

Hint: Descriptions always need triple quotes, not double [OK]

Common Mistakes:

• Using single or double quotes instead of triple quotes
• Placing descriptions after fields
• Assuming arguments need descriptions

5. You want to document a GraphQL schema so that the Book type and its title field have clear descriptions. Which schema snippet correctly documents both?

hard

A. "A book in the library" type Book { title: String "Title of the book" }

B. type Book { title: String """Title of the book""" } """A book in the library"""

C. type Book { "A book in the library" title: String "Title of the book" }

D. """A book in the library""" type Book { """Title of the book""" title: String }

Solution

1. Step 1: Check how to document a type

   The type description must be placed immediately before the type keyword using triple quotes.

2. Step 2: Check how to document a field

   The field description must be placed immediately before the field definition using triple quotes.

3. Step 3: Validate each option

   Only """A book in the library""" type Book { """Title of the book""" title: String } correctly places triple-quoted descriptions before the type and field.

4. Final Answer:

   """A book in the library""" type Book { """Title of the book""" title: String } -> Option D

5. Quick Check:

   Descriptions before type and field with triple quotes = correct [OK]

Hint: Put triple-quoted descriptions right before type and field [OK]

Common Mistakes:

• Placing descriptions after types or fields
• Using single quotes instead of triple quotes
• Not adding description for both type and field