diff --git a/.annotaterb.yml b/.annotaterb.yml
new file mode 100644
index 0000000..5c007f0
--- /dev/null
+++ b/.annotaterb.yml
@@ -0,0 +1,58 @@
+---
+:position: before
+:position_in_additional_file_patterns: before
+:position_in_class: before
+:position_in_factory: before
+:position_in_fixture: before
+:position_in_routes: before
+:position_in_serializer: before
+:position_in_test: before
+:classified_sort: true
+:exclude_controllers: true
+:exclude_factories: true
+:exclude_fixtures: false
+:exclude_helpers: true
+:exclude_scaffolds: true
+:exclude_serializers: false
+:exclude_sti_subclasses: false
+:exclude_tests: true
+:force: false
+:format_markdown: false
+:format_rdoc: false
+:format_yard: false
+:frozen: false
+:ignore_model_sub_dir: false
+:ignore_unknown_models: false
+:include_version: false
+:show_check_constraints: false
+:show_complete_foreign_keys: false
+:show_foreign_keys: true
+:show_indexes: true
+:simple_indexes: false
+:sort: false
+:timestamp: false
+:trace: false
+:with_comment: true
+:with_column_comments: true
+:with_table_comments: true
+:active_admin: false
+:command: 
+:debug: false
+:hide_default_column_types: ''
+:hide_limit_column_types: ''
+:ignore_columns: 
+:ignore_routes: 
+:models: true
+:routes: false
+:skip_on_db_migrate: false
+:target_action: :do_annotations
+:wrapper: 
+:wrapper_close: 
+:wrapper_open: 
+:classes_default_to_s: []
+:additional_file_patterns: []
+:model_dir:
+- app/models
+:require: []
+:root_dir:
+- ''
diff --git a/Gemfile b/Gemfile
index c64df42..83b5acf 100644
--- a/Gemfile
+++ b/Gemfile
@@ -22,6 +22,7 @@ gem 'react-rails'
 gem 'rubytree'
 
 group :development, :test do
+  gem 'annotaterb'
   gem 'debug', platforms: %i[mri windows]
   gem 'factory_bot_rails'
   gem 'license_finder'
diff --git a/Gemfile.lock b/Gemfile.lock
index fa7df0e..3d76af1 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -72,6 +72,7 @@ GEM
       securerandom (>= 0.3)
       tzinfo (~> 2.0, >= 2.0.5)
       uri (>= 0.13.1)
+    annotaterb (4.13.0)
     ast (2.4.2)
     babel-source (5.8.35)
     babel-transpiler (0.7.0)
@@ -341,6 +342,7 @@ PLATFORMS
   x86_64-linux
 
 DEPENDENCIES
+  annotaterb
   bootsnap
   chroma
   csv
diff --git a/app/controllers/groups_controller.rb b/app/controllers/groups_controller.rb
index 232ac85..37df884 100644
--- a/app/controllers/groups_controller.rb
+++ b/app/controllers/groups_controller.rb
@@ -2,7 +2,6 @@
 
 class GroupsController < ApplicationController
   def index
-    roots = Group.where(parent_id: nil)
-    render jsonapi: roots, include: [children: [children: [:children]]]
+    render json: Groups::SummaryQuery.new.call.as_json
   end
 end
diff --git a/app/models/expense.rb b/app/models/expense.rb
index 34e2e33..32f486f 100644
--- a/app/models/expense.rb
+++ b/app/models/expense.rb
@@ -1,4 +1,15 @@
 # Copyright (C) 2024 Manuel Bustillo
 
+# == Schema Information
+#
+# Table name: expenses
+#
+#  id           :uuid             not null, primary key
+#  amount       :decimal(, )
+#  name         :string
+#  pricing_type :enum             default("fixed"), not null
+#  created_at   :datetime         not null
+#  updated_at   :datetime         not null
+#
 class Expense < ApplicationRecord
 end
diff --git a/app/models/group.rb b/app/models/group.rb
index 105d08c..fe11e0b 100644
--- a/app/models/group.rb
+++ b/app/models/group.rb
@@ -1,5 +1,27 @@
 # Copyright (C) 2024 Manuel Bustillo
 
+# == Schema Information
+#
+# Table name: groups
+#
+#  id         :uuid             not null, primary key
+#  color      :string
+#  icon       :string
+#  name       :string           not null
+#  order      :integer          default(1), not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#  parent_id  :uuid
+#
+# Indexes
+#
+#  index_groups_on_name       (name) UNIQUE
+#  index_groups_on_parent_id  (parent_id)
+#
+# Foreign Keys
+#
+#  fk_rails_...  (parent_id => groups.id)
+#
 class Group < ApplicationRecord
   validates :name, uniqueness: true
   validates :name, :order, presence: true
@@ -30,6 +52,8 @@ class Group < ApplicationRecord
   private
 
   def set_color
+    return if color.present?
+
     new_color = "##{SecureRandom.hex(3)}".paint
     new_color = new_color.lighten(30) if new_color.dark?
     self.color = new_color
diff --git a/app/models/guest.rb b/app/models/guest.rb
index bfa1265..6b8f70e 100644
--- a/app/models/guest.rb
+++ b/app/models/guest.rb
@@ -1,5 +1,25 @@
 # Copyright (C) 2024 Manuel Bustillo
 
+# == Schema Information
+#
+# Table name: guests
+#
+#  id         :uuid             not null, primary key
+#  name       :string
+#  phone      :string
+#  status     :integer          default("considered")
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#  group_id   :uuid             not null
+#
+# Indexes
+#
+#  index_guests_on_group_id  (group_id)
+#
+# Foreign Keys
+#
+#  fk_rails_...  (group_id => groups.id)
+#
 class Guest < ApplicationRecord
   belongs_to :group
 
diff --git a/app/models/seat.rb b/app/models/seat.rb
index 8395b9c..1f3769c 100644
--- a/app/models/seat.rb
+++ b/app/models/seat.rb
@@ -1,5 +1,26 @@
 # Copyright (C) 2024 Manuel Bustillo
 
+# == Schema Information
+#
+# Table name: seats
+#
+#  id                    :uuid             not null, primary key
+#  table_number          :integer
+#  created_at            :datetime         not null
+#  updated_at            :datetime         not null
+#  guest_id              :uuid             not null
+#  tables_arrangement_id :uuid             not null
+#
+# Indexes
+#
+#  index_seats_on_guest_id               (guest_id)
+#  index_seats_on_tables_arrangement_id  (tables_arrangement_id)
+#
+# Foreign Keys
+#
+#  fk_rails_...  (guest_id => guests.id)
+#  fk_rails_...  (tables_arrangement_id => tables_arrangements.id) ON DELETE => cascade
+#
 class Seat < ApplicationRecord
   belongs_to :guest
   belongs_to :table_arrangement
diff --git a/app/models/tables_arrangement.rb b/app/models/tables_arrangement.rb
index d1eba03..6e2f621 100644
--- a/app/models/tables_arrangement.rb
+++ b/app/models/tables_arrangement.rb
@@ -1,5 +1,15 @@
 # Copyright (C) 2024 Manuel Bustillo
 
+# == Schema Information
+#
+# Table name: tables_arrangements
+#
+#  id         :uuid             not null, primary key
+#  discomfort :integer
+#  name       :string           not null
+#  created_at :datetime         not null
+#  updated_at :datetime         not null
+#
 class TablesArrangement < ApplicationRecord
   has_many :seats
   has_many :guests, through: :seats
diff --git a/app/queries/groups/summary_query.rb b/app/queries/groups/summary_query.rb
new file mode 100644
index 0000000..637a508
--- /dev/null
+++ b/app/queries/groups/summary_query.rb
@@ -0,0 +1,31 @@
+# Copyright (C) 2024 Manuel Bustillo
+
+module Groups
+  class SummaryQuery
+    def call
+      ActiveRecord::Base.connection.execute(query).to_a
+    end
+
+    private
+
+    def query
+      <<~SQL.squish
+        SELECT#{' '}
+          groups.id,
+          groups.name,
+          groups.icon,
+          groups.parent_id,
+          groups.color,
+          count(*) filter (where status IS NOT NULL) as total,
+          count(*) filter (where status = 0) as considered,
+          count(*) filter (where status = 10) as invited,
+          count(*) filter (where status = 20) as confirmed,
+          count(*) filter (where status = 30) as declined,
+          count(*) filter (where status = 40) as tentative
+        FROM groups
+        LEFT JOIN guests on groups.id = guests.group_id
+        GROUP BY groups.id
+      SQL
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index c54ec05..7107478 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -1,5 +1,3 @@
-# Copyright (C) 2024 Manuel Bustillo
-
 # This file is auto-generated from the current state of the database. Instead
 # of editing this file, please use the migrations feature of Active Record to
 # incrementally modify your database, and then regenerate this schema definition.
diff --git a/lib/tasks/annotate_rb.rake b/lib/tasks/annotate_rb.rake
new file mode 100644
index 0000000..1ad0ec3
--- /dev/null
+++ b/lib/tasks/annotate_rb.rake
@@ -0,0 +1,8 @@
+# This rake task was added by annotate_rb gem.
+
+# Can set `ANNOTATERB_SKIP_ON_DB_TASKS` to be anything to skip this
+if Rails.env.development? && ENV["ANNOTATERB_SKIP_ON_DB_TASKS"].nil?
+  require "annotate_rb"
+
+  AnnotateRb::Core.load_rake_tasks
+end
diff --git a/spec/queries/groups/summary_query_spec.rb b/spec/queries/groups/summary_query_spec.rb
new file mode 100644
index 0000000..6e2c3d2
--- /dev/null
+++ b/spec/queries/groups/summary_query_spec.rb
@@ -0,0 +1,98 @@
+# Copyright (C) 2024 Manuel Bustillo
+
+require 'rails_helper'
+
+module Groups
+  RSpec.describe SummaryQuery do
+    describe '#call' do
+      subject { described_class.new.call }
+
+      context 'when there are no groups' do
+        it { is_expected.to eq([]) }
+      end
+
+      context 'when groups are defined' do
+        let!(:parent) { create(:group, name: 'Friends', icon: 'icon-1', color: '#FF0000') }
+        let!(:child) { create(:group, name: 'Family', icon: 'icon-2', color: '#00FF00', parent:) }
+
+        context 'when there are no guests' do
+          it 'returns the summary of groups' do
+            is_expected.to contain_exactly(
+              { 'id' => parent.id,
+                'name' => 'Friends',
+                'icon' => 'icon-1',
+                'parent_id' => nil,
+                'color' => '#FF0000',
+                'total' => 0,
+                'considered' => 0,
+                'invited' => 0,
+                'confirmed' => 0,
+                'declined' => 0,
+                'tentative' => 0 },
+              { 'id' => child.id,
+                'name' => 'Family',
+                'icon' => 'icon-2',
+                'parent_id' => parent.id,
+                'color' => '#00FF00',
+                'total' => 0,
+                'considered' => 0,
+                'invited' => 0,
+                'confirmed' => 0,
+                'declined' => 0,
+                'tentative' => 0 }
+            )
+          end
+        end
+
+        context 'when there are guests' do
+          before do
+            # Parent group
+            create_list(:guest, 2, group: parent, status: :considered)
+            create_list(:guest, 3, group: parent, status: :invited)
+            create_list(:guest, 4, group: parent, status: :confirmed)
+            create_list(:guest, 5, group: parent, status: :declined)
+            create_list(:guest, 6, group: parent, status: :tentative)
+
+            # Child group
+            create_list(:guest, 7, group: child, status: :considered)
+            create_list(:guest, 8, group: child, status: :invited)
+            create_list(:guest, 9, group: child, status: :confirmed)
+            create_list(:guest, 10, group: child, status: :declined)
+            create_list(:guest, 11, group: child, status: :tentative)
+          end
+
+          it 'returns the summary of groups' do
+            is_expected.to contain_exactly(
+              {
+                'id' => parent.id,
+                'name' => 'Friends',
+                'icon' => 'icon-1',
+                'parent_id' => nil,
+                'color' => '#FF0000',
+                'total' => 20,
+                'considered' => 2,
+                'invited' => 3,
+                'confirmed' => 4,
+                'declined' => 5,
+                'tentative' => 6
+              },
+              {
+                'id' => child.id,
+                'name' => 'Family',
+                'icon' => 'icon-2',
+                'parent_id' => parent.id,
+                'color' => '#00FF00',
+                'total' => 45,
+                'considered' => 7,
+                'invited' => 8,
+                'confirmed' => 9,
+                'declined' => 10,
+                'tentative' => 11
+              }
+            )
+          end
+        end
+      end
+    end
+  end
+end