diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 1a3ad7f..3af89b7 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -30,7 +30,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        ruby-version: ['3.0', '3.1', '3.2', '3.3']
+        ruby-version: ['3.1', '3.2', '3.3']
 
     steps:
     - uses: actions/checkout@v4
diff --git a/.rubocop_todo.yml b/.rubocop_todo.yml
index 7552afe..79756fd 100644
--- a/.rubocop_todo.yml
+++ b/.rubocop_todo.yml
@@ -100,7 +100,7 @@ RSpec/DescribeClass:
 # Offense count: 4
 # Configuration parameters: CountAsOne.
 RSpec/ExampleLength:
-  Max: 172
+  Max: 186
 
 # Offense count: 24
 RSpec/LeakyConstantDeclaration:
diff --git a/CHANGELOG.md b/CHANGELOG.md
index c178658..cb310d6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,7 @@
 #### Fixes
 
 * Your contribution here.
+* [#75](https://github.com/ruby-grape/grape-swagger-entity/pull/75): Fix handling of entity with class names without "entity" or "entities" - [@numbata](https://github.com/numbata).
 
 ### 0.5.5 (2024/09/09)
 
diff --git a/lib/grape-swagger/entity/attribute_parser.rb b/lib/grape-swagger/entity/attribute_parser.rb
index 841a0c6..220f35e 100644
--- a/lib/grape-swagger/entity/attribute_parser.rb
+++ b/lib/grape-swagger/entity/attribute_parser.rb
@@ -5,6 +5,9 @@ module Entity
     class AttributeParser
       attr_reader :endpoint
 
+      # The list of that doesn't handled by `GrapeSwagger::DocMethods::DataType.primitive?` method
+      ADDITIONAL_PRIMITIVE_TYPES = %w[string array].freeze
+
       def initialize(endpoint)
         @endpoint = endpoint
       end
@@ -53,9 +56,15 @@ def direct_model_type?(type)
       end
 
       def ambiguous_model_type?(type)
-        type&.is_a?(Class) &&
-          !GrapeSwagger::DocMethods::DataType.primitive?(type.name.downcase) &&
-          !type == Array
+        type&.is_a?(Class) && !primitive_type?(type)
+      end
+
+      def primitive_type?(type)
+        type_name = type.name&.downcase
+        return false if type_name.nil?
+
+        GrapeSwagger::DocMethods::DataType.primitive?(type_name) ||
+          ADDITIONAL_PRIMITIVE_TYPES.include?(type_name)
       end
 
       def data_type_from(entity_options)
diff --git a/spec/grape-swagger/entities/response_model_spec.rb b/spec/grape-swagger/entities/response_model_spec.rb
index 298457c..33770ee 100644
--- a/spec/grape-swagger/entities/response_model_spec.rb
+++ b/spec/grape-swagger/entities/response_model_spec.rb
@@ -179,6 +179,16 @@ class Polymorphic < Grape::Entity
                                                }, documentation: { desc: 'Polymorphic Number', type: 'Integer' }
         end
 
+        class TagType < CustomType
+          def tags
+            %w[Cyan Magenta Yellow Key]
+          end
+        end
+
+        class MixedType < Grape::Entity
+          expose :tags, documentation: { type: TagType, desc: 'Tags', is_array: true }
+        end
+
         class SomeEntity < Grape::Entity
           expose :text, documentation: { type: 'string', desc: 'Content of something.' }
           expose :kind, using: Kind, documentation: { type: 'TheseApi_Kind', desc: 'The kind of this something.' }
@@ -190,7 +200,8 @@ class SomeEntity < Grape::Entity
           expose :values, using: TheseApi::Entities::Values, documentation: { desc: 'Tertiary kind.' }
           expose :nested, using: TheseApi::Entities::Nested, documentation: { desc: 'Nested object.' }
           expose :nested_child, using: TheseApi::Entities::NestedChild, documentation: { desc: 'Nested child object.' }
-          expose :polymorphic, using: TheseApi::Entities::Polymorphic, documentation: { desc: 'Polymorphic Model' }
+          expose :polymorphic, using: TheseApi::Entities::Polymorphic, documentation: { desc: 'A polymorphic model.' }
+          expose :mixed, using: TheseApi::Entities::MixedType, documentation: { desc: 'A model with mix of types.' }
           expose :merged_attribute, using: ThisApi::Entities::Nested, merge: true
         end
       end
@@ -365,6 +376,17 @@ def app
       }
     )
 
+    expect(subject['TheseApi_Entities_MixedType']).to eql(
+      'properties' => {
+        'tags' => {
+          'description' => 'Tags',
+          'items' => { '$ref' => '#/definitions/TheseApi_Entities_TagType' },
+          'type' => 'array'
+        }
+      },
+      'type' => 'object'
+    )
+
     expect(subject['TheseApi_Entities_SomeEntity']).to eql(
       'type' => 'object',
       'properties' => {
@@ -382,7 +404,11 @@ def app
         'code' => { 'type' => 'string', 'description' => 'Error code' },
         'message' => { 'type' => 'string', 'description' => 'Error message' },
         'polymorphic' => { '$ref' => '#/definitions/TheseApi_Entities_Polymorphic',
-                           'description' => 'Polymorphic Model' },
+                           'description' => 'A polymorphic model.' },
+        'mixed' => {
+          '$ref' => '#/definitions/TheseApi_Entities_MixedType',
+          'description' => 'A model with mix of types.'
+        },
         'attr' => { 'type' => 'string', 'description' => 'Attribute' }
       },
       'required' => %w[attr],
diff --git a/spec/grape-swagger/entity/attribute_parser_spec.rb b/spec/grape-swagger/entity/attribute_parser_spec.rb
index 99f9d71..c5686fe 100644
--- a/spec/grape-swagger/entity/attribute_parser_spec.rb
+++ b/spec/grape-swagger/entity/attribute_parser_spec.rb
@@ -35,6 +35,24 @@
           it { is_expected.to include(example: %w[green blue].map { { name: _1 } }) }
         end
 
+        context 'when the entity is implicit Entity' do
+          let(:entity_type) do
+            Class.new(ThisApi::Entities::Tag) do
+              def self.name
+                'ThisApi::Tag'
+              end
+
+              def self.to_s
+                name
+              end
+            end
+          end
+          let(:entity_options) { { documentation: { type: entity_type, is_array: true, min_items: 1 } } }
+
+          it { is_expected.to include('type' => 'array') }
+          it { is_expected.to include('items' => { '$ref' => '#/definitions/Tag' }) }
+        end
+
         context 'when it contains min_items' do
           let(:entity_options) { { using: ThisApi::Entities::Tag, documentation: { is_array: true, min_items: 1 } } }
 
diff --git a/spec/support/shared_contexts/custom_type_parser.rb b/spec/support/shared_contexts/custom_type_parser.rb
new file mode 100644
index 0000000..7095a07
--- /dev/null
+++ b/spec/support/shared_contexts/custom_type_parser.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+CustomType = Class.new
+
+class CustomTypeParser
+  attr_reader :model, :endpoint
+
+  def initialize(model, endpoint)
+    @model = model
+    @endpoint = endpoint
+  end
+
+  def call
+    {
+      model.name.to_sym => {
+        type: 'custom_type',
+        description: "it's a custom type",
+        data: {
+          name: model.name
+        }
+      }
+    }
+  end
+end
+
+GrapeSwagger.model_parsers.register(CustomTypeParser, CustomType)