diff --git a/graphql_parser/lib/src/language/ast/definition.dart b/graphql_parser/lib/src/language/ast/definition.dart
index efc72ee0..d129d422 100644
--- a/graphql_parser/lib/src/language/ast/definition.dart
+++ b/graphql_parser/lib/src/language/ast/definition.dart
@@ -1,9 +1,13 @@
 import 'node.dart';
 
+/// The base class for top-level GraphQL definitions.
 abstract class DefinitionContext extends Node {}
 
+/// An executable definition.
 abstract class ExecutableDefinitionContext extends DefinitionContext {}
 
+/// An ad-hoc type system declared in GraphQL.
 abstract class TypeSystemDefinitionContext extends DefinitionContext {}
 
+/// An extension to an existing ad-hoc type system.
 abstract class TypeSystemExtensionContext extends DefinitionContext {}