diff --git a/spec/rails/app/controllers/tables_controller.rb b/spec/rails/app/controllers/tables_controller.rb
index f43daa1c..f9d23bee 100644
--- a/spec/rails/app/controllers/tables_controller.rb
+++ b/spec/rails/app/controllers/tables_controller.rb
@@ -5,7 +5,11 @@ class TablesController < ApplicationController
 
   def index
     response.set_header('X-Cursor', 100)
-    render json: [find_table]
+    if params[:show_columns]
+      render json: [find_table('42')]
+    else
+      render json: [find_table]
+    end
   end
 
   def show
@@ -53,6 +57,24 @@ def find_table(id = nil)
         created_at: time.iso8601,
         updated_at: time.iso8601,
       }
+    when '42'
+      {
+        id: 42,
+        name: 'access',
+        description: 'logs',
+        database: {
+          id: 4242,
+          name: 'production',
+        },
+        columns: [
+          { name: 'id', column_type: 'integer' },
+          { name: 'description', column_type: 'varchar' }
+        ],
+        null_sample: nil,
+        storage_size: 12.3,
+        created_at: time.iso8601,
+        updated_at: time.iso8601,
+      }
     else
       raise NotFoundError
     end
diff --git a/spec/rails/doc/smart/expected.yaml b/spec/rails/doc/smart/expected.yaml
index dce47efd..e8b0bf64 100644
--- a/spec/rails/doc/smart/expected.yaml
+++ b/spec/rails/doc/smart/expected.yaml
@@ -36,6 +36,11 @@ paths:
         schema:
           type: integer
         example: 10
+      - name: show_columns
+        in: query
+        schema:
+          type: string
+        example: "true"
       responses:
         '200':
           description: with flat query parameters
@@ -46,16 +51,21 @@ paths:
                 items:
                   "$ref": "#/components/schemas/Table"
               example:
-              - id: 1
+              - id: 42
                 name: access
                 description: logs
                 database:
-                  id: 2
+                  id: 4242
                   name: production
                 null_sample:
                 storage_size: 12.3
                 created_at: '2020-07-17T00:00:00+00:00'
                 updated_at: '2020-07-17T00:00:00+00:00'
+                columns:
+                  - name: id
+                    column_type: integer
+                  - name: description
+                    column_type: varchar
           headers:
             X-Cursor:
               schema:
@@ -137,6 +147,10 @@ components:
           type: string
         database:
           "$ref": "#/components/schemas/Database"
+        columns:
+          type: array
+          items:
+            "$ref": "#/components/schemas/Column"
         null_sample:
           nullable: true
         storage_size:
@@ -155,3 +169,10 @@ components:
           description: 'this should be preserved'
         name:
           type: string
+    Column:
+      type: object
+      properties:
+        name:
+          type: string
+        column_type:
+          type: string
diff --git a/spec/rails/doc/smart/openapi.yaml b/spec/rails/doc/smart/openapi.yaml
index c608b5da..a4ed6de7 100644
--- a/spec/rails/doc/smart/openapi.yaml
+++ b/spec/rails/doc/smart/openapi.yaml
@@ -214,6 +214,10 @@ components:
           type: string
         database:
           "$ref": "#/components/schemas/Database"
+        columns:
+          type: array
+          items:
+            "$ref": "#/components/schemas/Column"
         null_sample:
           nullable: true
         storage_size:
diff --git a/spec/requests/rails_smart_merge_spec.rb b/spec/requests/rails_smart_merge_spec.rb
index 5d19b8d1..0cf1d20e 100644
--- a/spec/requests/rails_smart_merge_spec.rb
+++ b/spec/requests/rails_smart_merge_spec.rb
@@ -29,7 +29,7 @@
     context it 'returns a list of tables' do
       it 'with flat query parameters' do
         # These new params replace them in old spec
-        get '/tables', params: { page: '42', per: '10' },
+        get '/tables', params: { page: '42', per: '10', show_columns: true },
             headers: { authorization: 'k0kubun', "X-Authorization-Token": 'token' }
         response.set_header('X-Cursor', 100)
         expect(response.status).to eq(200)