diff --git a/.gitignore b/.gitignore
index 5fb66c9..13e3051 100644
--- a/.gitignore
+++ b/.gitignore
@@ -33,3 +33,6 @@
 
 # Ignore master key for decrypting credentials and more.
 /config/master.key
+
+# Ignore swagger generated documentation
+swagger/v1/swagger.yaml
diff --git a/Dockerfile.dev b/Dockerfile.dev
index 792a1ce..f911e52 100644
--- a/Dockerfile.dev
+++ b/Dockerfile.dev
@@ -1,7 +1,7 @@
 # syntax = docker/dockerfile:1
 
 # Make sure RUBY_VERSION matches the Ruby version in .ruby-version and Gemfile
-ARG RUBY_VERSION=3.3.5
+ARG RUBY_VERSION=3.3.6
 FROM registry.docker.com/library/ruby:$RUBY_VERSION-slim as base
 
 # Rails app lives here
diff --git a/Gemfile b/Gemfile
index e3f3306..81b24ff 100644
--- a/Gemfile
+++ b/Gemfile
@@ -28,6 +28,7 @@ group :development, :test do
   gem 'license_finder'
   gem 'pry'
   gem 'rspec-rails', '~> 7.1.0'
+  gem 'rswag'
   gem 'shoulda-matchers', '~> 6.0'
 end
 
diff --git a/Gemfile.lock b/Gemfile.lock
index 8b7b155..9667dfe 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -72,6 +72,8 @@ GEM
       securerandom (>= 0.3)
       tzinfo (~> 2.0, >= 2.0.5)
       uri (>= 0.13.1)
+    addressable (2.8.7)
+      public_suffix (>= 2.0.2, < 7.0)
     annotaterb (4.13.0)
     ast (2.4.2)
     babel-source (5.8.35)
@@ -127,6 +129,8 @@ GEM
       actionview (>= 5.0.0)
       activesupport (>= 5.0.0)
     json (2.7.5)
+    json-schema (5.0.1)
+      addressable (~> 2.8)
     jsonapi-deserializable (0.2.0)
     jsonapi-parser (0.1.1)
     jsonapi-rails (0.4.1)
@@ -195,6 +199,7 @@ GEM
       method_source (~> 1.0)
     psych (5.2.0)
       stringio
+    public_suffix (6.0.1)
     puma (6.4.3)
       nio4r (~> 2.0)
     raabro (1.4.0)
@@ -272,6 +277,21 @@ GEM
       rspec-mocks (~> 3.13)
       rspec-support (~> 3.13)
     rspec-support (3.13.1)
+    rswag (2.16.0)
+      rswag-api (= 2.16.0)
+      rswag-specs (= 2.16.0)
+      rswag-ui (= 2.16.0)
+    rswag-api (2.16.0)
+      activesupport (>= 5.2, < 8.1)
+      railties (>= 5.2, < 8.1)
+    rswag-specs (2.16.0)
+      activesupport (>= 5.2, < 8.1)
+      json-schema (>= 2.2, < 6.0)
+      railties (>= 5.2, < 8.1)
+      rspec-core (>= 2.14)
+    rswag-ui (2.16.0)
+      actionpack (>= 5.2, < 8.1)
+      railties (>= 5.2, < 8.1)
     rubocop (1.68.0)
       json (~> 2.3)
       language_server-protocol (>= 3.17.0)
@@ -362,6 +382,7 @@ DEPENDENCIES
   react-rails
   redis (>= 4.0.1)
   rspec-rails (~> 7.1.0)
+  rswag
   rubocop
   rubytree
   shoulda-matchers (~> 6.0)
diff --git a/README.md b/README.md
index 4d4f615..49752d5 100644
--- a/README.md
+++ b/README.md
@@ -68,6 +68,16 @@ Unit tests can be executed with
 bundle exec rspec
 ```
 
+## API documentation
+
+Generate the OpenAPI documentation with the command:
+
+```
+rake rswag:specs:swaggerize
+```
+
+The documentation is available in Swagger UI in http://libre-wedding-planner.app.localhost/api/api-docs/index.html. If testing the API through the UI, you will need to select the second server (which includes the `/api` path), intended for development.
+
 ## Contributing
 
 Contributions of all kinds (code, UX/UI, testing, translations, etc.) are welcome. The procedures to contribute are still being defined, but don't hesitate to reach out in case you want to participate.
diff --git a/app/queries/groups/summary_query.rb b/app/queries/groups/summary_query.rb
index 637a508..70fc234 100644
--- a/app/queries/groups/summary_query.rb
+++ b/app/queries/groups/summary_query.rb
@@ -10,7 +10,7 @@ module Groups
 
     def query
       <<~SQL.squish
-        SELECT#{' '}
+        SELECT
           groups.id,
           groups.name,
           groups.icon,
diff --git a/config/initializers/rswag_api.rb b/config/initializers/rswag_api.rb
new file mode 100644
index 0000000..5c46141
--- /dev/null
+++ b/config/initializers/rswag_api.rb
@@ -0,0 +1,16 @@
+# Copyright (C) 2024 Manuel Bustillo
+
+Rswag::Api.configure do |c|
+
+  # Specify a root folder where Swagger JSON files are located
+  # This is used by the Swagger middleware to serve requests for API descriptions
+  # NOTE: If you're using rswag-specs to generate Swagger, you'll need to ensure
+  # that it's configured to generate files in the same folder
+  c.openapi_root = Rails.root.to_s + '/swagger'
+
+  # Inject a lambda function to alter the returned Swagger prior to serialization
+  # The function will have access to the rack env for the current request
+  # For example, you could leverage this to dynamically assign the "host" property
+  #
+  #c.swagger_filter = lambda { |swagger, env| swagger['host'] = env['HTTP_HOST'] }
+end
diff --git a/config/initializers/rswag_ui.rb b/config/initializers/rswag_ui.rb
new file mode 100644
index 0000000..9540ca4
--- /dev/null
+++ b/config/initializers/rswag_ui.rb
@@ -0,0 +1,18 @@
+# Copyright (C) 2024 Manuel Bustillo
+
+Rswag::Ui.configure do |c|
+
+  # List the Swagger endpoints that you want to be documented through the
+  # swagger-ui. The first parameter is the path (absolute or relative to the UI
+  # host) to the corresponding endpoint and the second is a title that will be
+  # displayed in the document selector.
+  # NOTE: If you're using rspec-api to expose Swagger files
+  # (under openapi_root) as JSON or YAML endpoints, then the list below should
+  # correspond to the relative paths for those endpoints.
+
+  c.swagger_endpoint '/api/api-docs/v1/swagger.yaml', 'API V1 Docs'
+
+  # Add Basic Auth in case your API is private
+  # c.basic_auth_enabled = true
+  # c.basic_auth_credentials 'username', 'password'
+end
diff --git a/config/routes.rb b/config/routes.rb
index 7e40865..80aa2e0 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -1,6 +1,8 @@
 # Copyright (C) 2024 Manuel Bustillo
 
 Rails.application.routes.draw do
+  mount Rswag::Ui::Engine => '/api-docs'
+  mount Rswag::Api::Engine => '/api-docs'
   resources :groups, only: :index
   resources :guests, only: %i[index update] do
     post :bulk_update, on: :collection
diff --git a/spec/requests/groups_spec.rb b/spec/requests/groups_spec.rb
new file mode 100644
index 0000000..8bf622b
--- /dev/null
+++ b/spec/requests/groups_spec.rb
@@ -0,0 +1,32 @@
+# Copyright (C) 2024 Manuel Bustillo
+
+require 'swagger_helper'
+
+RSpec.describe 'groups', type: :request do
+  path '/groups' do
+    get('list groups') do
+      produces 'application/json'
+      response(200, 'successful') do
+        schema type: :array,
+               items: {
+                 type: :object,
+                 required: %i[id name icon parent_id color total considered invited confirmed declined tentative],
+                 properties: {
+                   id: { type: :string, format: :uuid, required: true },
+                   name: { type: :string },
+                   icon: { type: :string, example: 'pi pi-crown', description: 'The CSS classes used by the icon' },
+                   parent_id: { type: :string, format: :uuid },
+                   color: { type: :string, pattern: '^#(?:[0-9a-fA-F]{3}){1,2}$' },
+                   total: { type: :integer, minimum: 0, description: 'Total number of guests in any status' },
+                   considered: { type: :integer, minimum: 0 },
+                   invited: { type: :integer, minimum: 0 },
+                   confirmed: { type: :integer, minimum: 0 },
+                   declined: { type: :integer, minimum: 0 },
+                   tentative: { type: :integer, minimum: 0 }
+                 }
+               }
+        run_test!
+      end
+    end
+  end
+end
diff --git a/spec/swagger_helper.rb b/spec/swagger_helper.rb
new file mode 100644
index 0000000..d07a97e
--- /dev/null
+++ b/spec/swagger_helper.rb
@@ -0,0 +1,45 @@
+# Copyright (C) 2024 Manuel Bustillo
+
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.configure do |config|
+  # Specify a root folder where Swagger JSON files are generated
+  # NOTE: If you're using the rswag-api to serve API descriptions, you'll need
+  # to ensure that it's configured to serve Swagger from the same folder
+  config.openapi_root = Rails.root.join('swagger').to_s
+
+  # Define one or more Swagger documents and provide global metadata for each one
+  # When you run the 'rswag:specs:swaggerize' rake task, the complete Swagger will
+  # be generated at the provided relative path under openapi_root
+  # By default, the operations defined in spec files are added to the first
+  # document below. You can override this behavior by adding a openapi_spec tag to the
+  # the root example_group in your specs, e.g. describe '...', openapi_spec: 'v2/swagger.json'
+  config.openapi_specs = {
+    'v1/swagger.yaml' => {
+      openapi: '3.0.1',
+      info: {
+        title: 'API V1',
+        version: 'v1'
+      },
+      paths: {},
+      servers: [
+        {
+          url: '/',
+          description: 'suitable for testing'
+        },
+        {
+          url: 'http://libre-wedding-planner.app.localhost/api',
+          description: 'Suitable for development'
+        }
+      ]
+    }
+  }
+
+  # Specify the format of the output Swagger file when running 'rswag:specs:swaggerize'.
+  # The openapi_specs configuration option has the filename including format in
+  # the key, this may want to be changed to avoid putting yaml in json files.
+  # Defaults to json. Accepts ':json' and ':yaml'.
+  config.openapi_format = :yaml
+end