Types are used throughout GraphQL to describe both the values accepted as input to arguments and variables as well as the values output by fields.

Fields are conceptually functions which return values, and occasionally accept arguments which alter their behavior.

The two keywords true and false represent the two boolean values.

Directives provide a way to describe alternate runtime execution and type validation behavior in a GraphQL document.

A GraphQL schema describes directives which are used to annotate various parts of a GraphQL document as an indicator that they should be evaluated differently by a validator, executor, or client tool such as a code generator.

A GraphQL Document describes a complete file or request string operated on by a GraphQL service or client.

GraphQL Enum types, like Scalar types, also represent leaf values in a GraphQL type system.

Enum type extensions are used to represent an enum type which has been extended from some original enum type.

Enum values are represented as unquoted names (ex.

A selection set is primarily composed of fields.

A FloatValue includes either a decimal point (ex.

Fragments are the primary unit of composition in GraphQL.

Fragments can be defined inline within a selection set.

Fields may accept arguments to configure their behavior.

Input object type extensions are used to represent an input object type which has been extended from some original input object type.

Object fields are conceptually functions which yield values.

GraphQL interfaces represent a list of named fields and their arguments.

Interface type extensions are used to represent an interface which has been extended from some original interface.

An IntValue is specified without a decimal point or exponent but may be negative (ex.

Lists are ordered sequences of values wrapped in square‐brackets [ ].

NullValue.

GraphQL queries are hierarchical and composed, describing a tree of information.

Object type extensions are used to represent a type which has been extended from some original type.

Input object literal values are unordered lists of keyed input values wrapped in curly‐braces { }.

Each operation is represented by an optional operation name and a selection set.

A schema defines the initial root operation type for each kind of operation it supports: query, mutation, and subscription; this determines the place in the type system where those operations begin.

Scalar types represent primitive leaf values in a GraphQL type system.

Scalar type extensions are used to represent a scalar type which has been extended from some original scalar type.

A GraphQL service’s collective type system capabilities are referred to as that service’s “schema”.

Schema extensions are used to represent a schema which has been extended from an original schema.

An operation selects the set of information it needs, and will receive exactly that information and nothing more, avoiding over‐fetching and under‐fetching data.

Strings are sequences of characters wrapped in quotation marks (U+0022).

GraphQL Unions represent an object that could be one of a list of GraphQL Object types, but provides for no guaranteed fields between those types.

Union type extensions are used to represent a union type which has been extended from some original union type.

A GraphQL query can be parameterized with variables, maximizing query reuse, and avoiding costly string building in clients at runtime.

Documentation is a first‐class feature of GraphQL type systems.

GraphQL describes the types of data expected by query variables.

The fundamental unit of any GraphQL Schema is the type.

Operation extensions are used to represent a GraphQL type which has been extended from some original type.

The GraphQL Operation system describes the capabilities of a GraphQL server and is used to determine if a query is valid.

Operation system extensions are used to represent a GraphQL type system which has been extended from some original type system.

Field and directive arguments accept input values of various literal primitives; input values can be scalars, enumeration values, lists, or input objects.

All of the types so far are assumed to be both nullable and singular: e.g.

There are three types of operations that GraphQL models: query – a read‐only fetch.