diff --git a/.github/workflows/restful-api.yml b/.github/workflows/ruby-on-rails--restful-api.yml
similarity index 86%
rename from .github/workflows/restful-api.yml
rename to .github/workflows/ruby-on-rails--restful-api.yml
index 9ec00879..3d708ab9 100644
--- a/.github/workflows/restful-api.yml
+++ b/.github/workflows/ruby-on-rails--restful-api.yml
@@ -5,7 +5,7 @@
 # This workflow will install a prebuilt Ruby version, install dependencies, and
 # run tests and linters.
 
-name: RESTful API
+name: Ruby on Rails - RESTful API
 
 on:
   push:
@@ -21,9 +21,9 @@ on:
       - ruby-on-rails/restful-api/Rakefile
       - ruby-on-rails/restful-api/.rubocop.yml
       - ruby-on-rails/restful-api/.rubocop_todo.yml
-      # - ruby-on-rails/restful-api/Steepfile
+      - ruby-on-rails/restful-api/Steepfile
       - ruby-on-rails/restful-api/**/*.rb
-      # - ruby-on-rails/restful-api/**/*.rbs
+      - ruby-on-rails/restful-api/**/*.rbs
       - ruby-on-rails/restful-api/**/*.rake
       - ruby-on-rails/restful-api/**/*.yml
   pull_request:
@@ -37,9 +37,9 @@ on:
       - ruby-on-rails/restful-api/Rakefile
       - ruby-on-rails/restful-api/.rubocop.yml
       - ruby-on-rails/restful-api/.rubocop_todo.yml
-      # - ruby-on-rails/restful-api/Steepfile
+      - ruby-on-rails/restful-api/Steepfile
       - ruby-on-rails/restful-api/**/*.rb
-      # - ruby-on-rails/restful-api/**/*.rbs
+      - ruby-on-rails/restful-api/**/*.rbs
       - ruby-on-rails/restful-api/**/*.rake
       - ruby-on-rails/restful-api/**/*.yml
 
@@ -53,7 +53,7 @@ jobs:
     outputs:
       ruby-changes: ${{ steps.change-detection.outputs.ruby }}
       rubocop-changes: ${{ steps.change-detection.outputs.rubocop}}
-      # steep-changes: ${{ steps.change-detection.outputs.steep}}
+      steep-changes: ${{ steps.change-detection.outputs.steep}}
     steps:
       - uses: actions/checkout@v6
       - name: Change Detection
@@ -148,19 +148,19 @@ jobs:
       - name: RuboCop
         working-directory: ./ruby-on-rails/restful-api
         run: bundle exec rubocop
-  # steep:
-  #   timeout-minutes: 10
-  #   runs-on: ubuntu-latest
-  #   needs: change-detection
-  #   if: needs.change-detection.outputs.steep-changes == 'true'
-  #   steps:
-  #     - uses: actions/checkout@v6
-  #     - uses: ./.github/actions/setup-ruby-on-rails
-  #       with:
-  #         working-directory: ./ruby-on-rails/restful-api
-  #         job-name: steep
-  #     - name: Steep
-  #       working-directory: ./ruby-on-rails/restful-api
-  #       run: |
-  #         bundle exec rbs-inline --output sig/generated/ .
-  #         bundle exec steep check
+  steep:
+    timeout-minutes: 10
+    runs-on: ubuntu-latest
+    needs: change-detection
+    if: needs.change-detection.outputs.steep-changes == 'true'
+    steps:
+      - uses: actions/checkout@v6
+      - uses: ./.github/actions/setup-ruby-on-rails
+        with:
+          working-directory: ./ruby-on-rails/restful-api
+          job-name: steep
+      - name: Steep
+        working-directory: ./ruby-on-rails/restful-api
+        run: |
+          bundle exec rbs-inline --output sig/generated/ .
+          bundle exec steep check
diff --git a/ruby-on-rails/restful-api/Gemfile b/ruby-on-rails/restful-api/Gemfile
index ec2cb2d5..54094020 100644
--- a/ruby-on-rails/restful-api/Gemfile
+++ b/ruby-on-rails/restful-api/Gemfile
@@ -33,8 +33,6 @@ gem 'will_paginate', '~> 4.0.1'
 # environmental variables
 gem 'dotenv-rails', '~> 3.2.0'
 
-gem 'nokogiri', '~> 1.19.3'
-
 gem 'net-smtp', '~> 0.5.0'
 
 # The Observer pattern provides a simple mechanism for one object to inform a set of interested third-party objects when its state changes.
@@ -43,9 +41,6 @@ gem 'observer', '~> 0.1.2'
 # Data structure, similar to a Hash, that allows the definition of arbitrary attributes with their accompanying values
 gem 'ostruct', '~> 0.6.3'
 
-# A foreign function interface (FFI) is a mechanism by which a program written in one programming language can call routines or make use of services written or compiled in another one
-gem 'ffi', '~> 1.17.4'
-
 group :development, :test do
   # Debug tool used with binding.irb. Explicit require avoids eager loading `debug/prelude`
   # which interferes with the Docker boot process.
@@ -62,6 +57,9 @@ group :development do
   gem 'rubocop-performance', '~> 1.26.0', require: false
   gem 'rubocop-rails', '~> 2.34.3', require: false
   gem 'rubocop-rspec', '~> 3.9.0', require: false
+  # Typechecking
+  gem 'rbs-inline', '~> 0.13.0', require: false
+  gem 'steep', '~> 1.10.0', require: false
 end
 
 group :test do
diff --git a/ruby-on-rails/restful-api/Gemfile.lock b/ruby-on-rails/restful-api/Gemfile.lock
index 4a296778..b14a0cae 100644
--- a/ruby-on-rails/restful-api/Gemfile.lock
+++ b/ruby-on-rails/restful-api/Gemfile.lock
@@ -94,6 +94,7 @@ GEM
     concurrent-ruby (1.3.6)
     connection_pool (3.0.2)
     crass (1.0.6)
+    csv (3.3.5)
     database_cleaner (2.1.0)
       database_cleaner-active_record (>= 2, < 3)
     database_cleaner-active_record (2.2.2)
@@ -119,8 +120,8 @@ GEM
       railties (>= 6.1.0)
     faker (3.8.0)
       i18n (>= 1.8.11, < 2)
-    ffi (1.17.4)
     ffi (1.17.4-x86_64-linux-gnu)
+    fileutils (1.8.0)
     globalid (1.3.0)
       activesupport (>= 6.1)
     i18n (1.14.8)
@@ -137,6 +138,10 @@ GEM
       base64
     language_server-protocol (3.17.0.5)
     lint_roller (1.1.0)
+    listen (3.10.0)
+      logger
+      rb-fsevent (~> 0.10, >= 0.10.3)
+      rb-inotify (~> 0.9, >= 0.9.10)
     logger (1.7.0)
     loofah (2.25.1)
       crass (~> 1.0.2)
@@ -153,6 +158,7 @@ GEM
       drb (~> 2.0)
       prism (~> 1.5)
     msgpack (1.8.0)
+    mutex_m (0.3.0)
     mysql2 (0.5.7)
       bigdecimal
     net-imap (0.6.4)
@@ -223,6 +229,15 @@ GEM
       zeitwerk (~> 2.6)
     rainbow (3.1.1)
     rake (13.4.2)
+    rb-fsevent (0.11.2)
+    rb-inotify (0.11.1)
+      ffi (~> 1.0)
+    rbs (3.10.4)
+      logger
+      tsort
+    rbs-inline (0.13.0)
+      prism (>= 0.29)
+      rbs (>= 3.8.0)
     rdoc (7.2.0)
       erb
       psych (>= 4.0.0)
@@ -278,7 +293,27 @@ GEM
     securerandom (0.4.1)
     shoulda-matchers (7.0.1)
       activesupport (>= 7.1)
+    steep (1.10.0)
+      activesupport (>= 5.1)
+      concurrent-ruby (>= 1.1.10)
+      csv (>= 3.0.9)
+      fileutils (>= 1.1.0)
+      json (>= 2.1.0)
+      language_server-protocol (>= 3.17.0.4, < 4.0)
+      listen (~> 3.0)
+      logger (>= 1.3.0)
+      mutex_m (>= 0.3.0)
+      parser (>= 3.1)
+      rainbow (>= 2.2.2, < 4.0)
+      rbs (~> 3.9)
+      securerandom (>= 0.1)
+      strscan (>= 1.0.0)
+      terminal-table (>= 2, < 5)
+      uri (>= 0.12.0)
     stringio (3.2.0)
+    strscan (3.1.8)
+    terminal-table (4.0.0)
+      unicode-display_width (>= 1.1.1, < 4)
     thor (1.5.0)
     timeout (0.6.1)
     tsort (0.2.0)
@@ -309,21 +344,21 @@ DEPENDENCIES
   dotenv-rails (~> 3.2.0)
   factory_bot_rails (~> 6.5.1)
   faker (~> 3.8.0)
-  ffi (~> 1.17.4)
   jwt (~> 3.1.2)
   mysql2 (~> 0.5.7)
   net-smtp (~> 0.5.0)
-  nokogiri (~> 1.19.3)
   observer (~> 0.1.2)
   ostruct (~> 0.6.3)
   puma (~> 8.0.1)
   rails (~> 8.1.3)
+  rbs-inline (~> 0.13.0)
   rspec-rails (~> 8.0.4)
   rubocop (~> 1.86.1)
   rubocop-performance (~> 1.26.0)
   rubocop-rails (~> 2.34.3)
   rubocop-rspec (~> 3.9.0)
   shoulda-matchers (~> 7.0.1)
+  steep (~> 1.10.0)
   tzinfo-data
   will_paginate (~> 4.0.1)
 
@@ -353,6 +388,7 @@ CHECKSUMS
   concurrent-ruby (1.3.6) sha256=6b56837e1e7e5292f9864f34b69c5a2cbc75c0cf5338f1ce9903d10fa762d5ab
   connection_pool (3.0.2) sha256=33fff5ba71a12d2aa26cb72b1db8bba2a1a01823559fb01d29eb74c286e62e0a
   crass (1.0.6) sha256=dc516022a56e7b3b156099abc81b6d2b08ea1ed12676ac7a5657617f012bd45d
+  csv (3.3.5) sha256=6e5134ac3383ef728b7f02725d9872934f523cb40b961479f69cf3afa6c8e73f
   database_cleaner (2.1.0) sha256=1dcba26e3b1576da692fc6bac10136a4744da5bcc293d248aae19640c65d89cd
   database_cleaner-active_record (2.2.2) sha256=88296b9f3088c31f7c0d4fcec10f68e4b71c96698043916de59b04debec10388
   database_cleaner-core (2.0.1) sha256=8646574c32162e59ed7b5258a97a208d3c44551b854e510994f24683865d846c
@@ -367,8 +403,8 @@ CHECKSUMS
   factory_bot (6.5.6) sha256=12beb373214dccc086a7a63763d6718c49769d5606f0501e0a4442676917e077
   factory_bot_rails (6.5.1) sha256=d3cc4851eae4dea8a665ec4a4516895045e710554d2b5ac9e68b94d351bc6d68
   faker (3.8.0) sha256=c147b308df73a90f27a4fc84f18d4c22ef0ad9c2a64b2b61c86fd0ca71753efc
-  ffi (1.17.4) sha256=bcd1642e06f0d16fc9e09ac6d49c3a7298b9789bcb58127302f934e437d60acf
   ffi (1.17.4-x86_64-linux-gnu) sha256=9d3db14c2eae074b382fa9c083fe95aec6e0a1451da249eab096c34002bc752d
+  fileutils (1.8.0) sha256=8c6b1df54e2540bdb2f39258f08af78853aa70bad52b4d394bbc6424593c6e02
   globalid (1.3.0) sha256=05c639ad6eb4594522a0b07983022f04aa7254626ab69445a0e493aa3786ff11
   i18n (1.14.8) sha256=285778639134865c5e0f6269e0b818256017e8cde89993fdfcbfb64d088824a5
   io-console (0.8.2) sha256=d6e3ae7a7cc7574f4b8893b4fca2162e57a825b223a177b7afa236c5ef9814cc
@@ -378,6 +414,7 @@ CHECKSUMS
   jwt (3.1.2) sha256=af6991f19a6bb4060d618d9add7a66f0eeb005ac0bc017cd01f63b42e122d535
   language_server-protocol (3.17.0.5) sha256=fd1e39a51a28bf3eec959379985a72e296e9f9acfce46f6a79d31ca8760803cc
   lint_roller (1.1.0) sha256=2c0c845b632a7d172cb849cc90c1bce937a28c5c8ccccb50dfd46a485003cc87
+  listen (3.10.0) sha256=c6e182db62143aeccc2e1960033bebe7445309c7272061979bb098d03760c9d2
   logger (1.7.0) sha256=196edec7cc44b66cfb40f9755ce11b392f21f7967696af15d274dde7edff0203
   loofah (2.25.1) sha256=d436c73dbd0c1147b16c4a41db097942d217303e1f7728704b37e4df9f6d2e04
   mail (2.9.0) sha256=6fa6673ecd71c60c2d996260f9ee3dd387d4673b8169b502134659ece6d34941
@@ -385,6 +422,7 @@ CHECKSUMS
   mini_mime (1.1.5) sha256=8681b7e2e4215f2a159f9400b5816d85e9d8c6c6b491e96a12797e798f8bccef
   minitest (6.0.6) sha256=153ea36d1d987a62942382b61075745042a2b3123b1cd48f4c3675af9cc7d6f1
   msgpack (1.8.0) sha256=e64ce0212000d016809f5048b48eb3a65ffb169db22238fb4b72472fecb2d732
+  mutex_m (0.3.0) sha256=cfcb04ac16b69c4813777022fdceda24e9f798e48092a2b817eb4c0a782b0751
   mysql2 (0.5.7) sha256=ba09ede515a0ae8a7192040a1b778c0fb0f025fa5877e9be895cd325fa5e9d7b
   net-imap (0.6.4) sha256=9a5598c67a3022c284d98430ef1d4948e7dbdb62596f61081ea8ca933270a02b
   net-pop (0.1.2) sha256=848b4e982013c15b2f0382792268763b748cce91c9e91e36b0f27ed26420dff3
@@ -412,6 +450,10 @@ CHECKSUMS
   railties (8.1.3) sha256=913eb0e0cb520aac687ffd74916bd726d48fa21f47833c6292576ef6a286de22
   rainbow (3.1.1) sha256=039491aa3a89f42efa1d6dec2fc4e62ede96eb6acd95e52f1ad581182b79bc6a
   rake (13.4.2) sha256=cb825b2bd5f1f8e91ca37bddb4b9aaf345551b4731da62949be002fa89283701
+  rb-fsevent (0.11.2) sha256=43900b972e7301d6570f64b850a5aa67833ee7d87b458ee92805d56b7318aefe
+  rb-inotify (0.11.1) sha256=a0a700441239b0ff18eb65e3866236cd78613d6b9f78fea1f9ac47a85e47be6e
+  rbs (3.10.4) sha256=b17d7c4be4bb31a11a3b529830f0aa206a807ca42f2e7921a3027dfc6b7e5ce8
+  rbs-inline (0.13.0) sha256=aba6e48c2d1b75276e8557376164f4b4ba96dd0204e779a5cee2af442bd30442
   rdoc (7.2.0) sha256=8650f76cd4009c3b54955eb5d7e3a075c60a57276766ebf36f9085e8c9f23192
   regexp_parser (2.12.0) sha256=35a916a1d63190ab5c9009457136ae5f3c0c7512d60291d0d1378ba18ce08ebb
   reline (0.6.3) sha256=1198b04973565b36ec0f11542ab3f5cfeeec34823f4e54cebde90968092b1835
@@ -428,7 +470,10 @@ CHECKSUMS
   ruby-progressbar (1.13.0) sha256=80fc9c47a9b640d6834e0dc7b3c94c9df37f08cb072b7761e4a71e22cff29b33
   securerandom (0.4.1) sha256=cc5193d414a4341b6e225f0cb4446aceca8e50d5e1888743fac16987638ea0b1
   shoulda-matchers (7.0.1) sha256=b4bfd8744c10e0a36c8ac1a687f921ee7e25ed529e50488d61b79a8688749c77
+  steep (1.10.0) sha256=1b295b55f9aaff1b8d3ee42453ee55bc2a1078fda0268f288edb2dc014f4d7d1
   stringio (3.2.0) sha256=c37cb2e58b4ffbd33fe5cd948c05934af997b36e0b6ca6fdf43afa234cf222e1
+  strscan (3.1.8) sha256=aae2db611a225559f21ffbb71765c9a4e60fd262534a9ea84f4f11c7f32f679e
+  terminal-table (4.0.0) sha256=f504793203f8251b2ea7c7068333053f0beeea26093ec9962e62ea79f94301d2
   thor (1.5.0) sha256=e3a9e55fe857e44859ce104a84675ab6e8cd59c650a49106a05f55f136425e73
   timeout (0.6.1) sha256=78f57368a7e7bbadec56971f78a3f5ecbcfb59b7fcbb0a3ed6ddc08a5094accb
   tsort (0.2.0) sha256=9650a793f6859a43b6641671278f79cfead60ac714148aabe4e3f0060480089f
diff --git a/ruby-on-rails/restful-api/Steepfile b/ruby-on-rails/restful-api/Steepfile
new file mode 100644
index 00000000..d43294ff
--- /dev/null
+++ b/ruby-on-rails/restful-api/Steepfile
@@ -0,0 +1,11 @@
+D = Steep::Diagnostic
+
+target :app do
+  check "app"
+  check "spec"
+  signature "sig"
+
+  library "net-smtp"
+
+  configure_code_diagnostics(D::Ruby.default)
+end
diff --git a/ruby-on-rails/restful-api/app/auth/authenticate_user.rb b/ruby-on-rails/restful-api/app/auth/authenticate_user.rb
index a6943db3..5837fa75 100644
--- a/ruby-on-rails/restful-api/app/auth/authenticate_user.rb
+++ b/ruby-on-rails/restful-api/app/auth/authenticate_user.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class AuthenticateUser
   def initialize(email, password)
     @email = email
diff --git a/ruby-on-rails/restful-api/app/auth/authorize_api_request.rb b/ruby-on-rails/restful-api/app/auth/authorize_api_request.rb
index 3582cbe3..5c2bc3a4 100644
--- a/ruby-on-rails/restful-api/app/auth/authorize_api_request.rb
+++ b/ruby-on-rails/restful-api/app/auth/authorize_api_request.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class AuthorizeApiRequest
   def initialize(headers = {})
     @headers = headers
diff --git a/ruby-on-rails/restful-api/app/channels/application_cable/channel.rb b/ruby-on-rails/restful-api/app/channels/application_cable/channel.rb
index d6726972..3376ec25 100644
--- a/ruby-on-rails/restful-api/app/channels/application_cable/channel.rb
+++ b/ruby-on-rails/restful-api/app/channels/application_cable/channel.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 module ApplicationCable
   class Channel < ActionCable::Channel::Base
   end
diff --git a/ruby-on-rails/restful-api/app/channels/application_cable/connection.rb b/ruby-on-rails/restful-api/app/channels/application_cable/connection.rb
index 0ff5442f..feda2e8b 100644
--- a/ruby-on-rails/restful-api/app/channels/application_cable/connection.rb
+++ b/ruby-on-rails/restful-api/app/channels/application_cable/connection.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 module ApplicationCable
   class Connection < ActionCable::Connection::Base
   end
diff --git a/ruby-on-rails/restful-api/app/controllers/application_controller.rb b/ruby-on-rails/restful-api/app/controllers/application_controller.rb
index 9467a2ac..da8e2adb 100644
--- a/ruby-on-rails/restful-api/app/controllers/application_controller.rb
+++ b/ruby-on-rails/restful-api/app/controllers/application_controller.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class ApplicationController < ActionController::API
   include Response
   include ExceptionHandler
diff --git a/ruby-on-rails/restful-api/app/controllers/authentication_controller.rb b/ruby-on-rails/restful-api/app/controllers/authentication_controller.rb
index 1c572e69..c041c7c0 100644
--- a/ruby-on-rails/restful-api/app/controllers/authentication_controller.rb
+++ b/ruby-on-rails/restful-api/app/controllers/authentication_controller.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class AuthenticationController < ApplicationController
   skip_before_action :authorize_request, only: :authenticate
 
diff --git a/ruby-on-rails/restful-api/app/controllers/concerns/exception_handler.rb b/ruby-on-rails/restful-api/app/controllers/concerns/exception_handler.rb
index 79cf4e50..1afec114 100644
--- a/ruby-on-rails/restful-api/app/controllers/concerns/exception_handler.rb
+++ b/ruby-on-rails/restful-api/app/controllers/concerns/exception_handler.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 module ExceptionHandler
   extend ActiveSupport::Concern
 
diff --git a/ruby-on-rails/restful-api/app/controllers/concerns/response.rb b/ruby-on-rails/restful-api/app/controllers/concerns/response.rb
index cfb0caa4..5679d147 100644
--- a/ruby-on-rails/restful-api/app/controllers/concerns/response.rb
+++ b/ruby-on-rails/restful-api/app/controllers/concerns/response.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 module Response
   def json_response(object, status = :ok)
     render json: object, status: status
diff --git a/ruby-on-rails/restful-api/app/controllers/users_controller.rb b/ruby-on-rails/restful-api/app/controllers/users_controller.rb
index 8fd3e176..adebbfa9 100644
--- a/ruby-on-rails/restful-api/app/controllers/users_controller.rb
+++ b/ruby-on-rails/restful-api/app/controllers/users_controller.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class UsersController < ApplicationController
   skip_before_action :authorize_request, only: :create
 
diff --git a/ruby-on-rails/restful-api/app/controllers/v1/items_controller.rb b/ruby-on-rails/restful-api/app/controllers/v1/items_controller.rb
index 4df64e01..78985e60 100644
--- a/ruby-on-rails/restful-api/app/controllers/v1/items_controller.rb
+++ b/ruby-on-rails/restful-api/app/controllers/v1/items_controller.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class V1::ItemsController < ApplicationController
   before_action :set_todo
   before_action :set_todo_item, only: %i(show update destroy)
diff --git a/ruby-on-rails/restful-api/app/controllers/v1/todos_controller.rb b/ruby-on-rails/restful-api/app/controllers/v1/todos_controller.rb
index 425d0aa7..bad5ff89 100644
--- a/ruby-on-rails/restful-api/app/controllers/v1/todos_controller.rb
+++ b/ruby-on-rails/restful-api/app/controllers/v1/todos_controller.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class V1::TodosController < ApplicationController
   before_action :set_todo, only: %i(show update destroy)
 
diff --git a/ruby-on-rails/restful-api/app/controllers/v2/todos_controller.rb b/ruby-on-rails/restful-api/app/controllers/v2/todos_controller.rb
index d30b9e1f..52713219 100644
--- a/ruby-on-rails/restful-api/app/controllers/v2/todos_controller.rb
+++ b/ruby-on-rails/restful-api/app/controllers/v2/todos_controller.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class V2::TodosController < ApplicationController
   def index
     # a dummy response
diff --git a/ruby-on-rails/restful-api/app/jobs/application_job.rb b/ruby-on-rails/restful-api/app/jobs/application_job.rb
index d394c3d1..8c2a02f9 100644
--- a/ruby-on-rails/restful-api/app/jobs/application_job.rb
+++ b/ruby-on-rails/restful-api/app/jobs/application_job.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class ApplicationJob < ActiveJob::Base
   # Automatically retry jobs that encountered a deadlock
   # retry_on ActiveRecord::Deadlocked
diff --git a/ruby-on-rails/restful-api/app/lib/api_version.rb b/ruby-on-rails/restful-api/app/lib/api_version.rb
index 01b3e254..f82866c9 100644
--- a/ruby-on-rails/restful-api/app/lib/api_version.rb
+++ b/ruby-on-rails/restful-api/app/lib/api_version.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class ApiVersion
   attr_reader :version, :default
 
diff --git a/ruby-on-rails/restful-api/app/lib/concerns/exception_handler.rb b/ruby-on-rails/restful-api/app/lib/concerns/exception_handler.rb
index 7eb38b8e..ef79b4e5 100644
--- a/ruby-on-rails/restful-api/app/lib/concerns/exception_handler.rb
+++ b/ruby-on-rails/restful-api/app/lib/concerns/exception_handler.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 module ExceptionHandler
   extend ActiveSupport::Concern
 
diff --git a/ruby-on-rails/restful-api/app/lib/json_web_token.rb b/ruby-on-rails/restful-api/app/lib/json_web_token.rb
index 6a4d63a1..3264f38b 100644
--- a/ruby-on-rails/restful-api/app/lib/json_web_token.rb
+++ b/ruby-on-rails/restful-api/app/lib/json_web_token.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class JsonWebToken
   # secret to encode and decode token
   HMAC_SECRET = Rails.application.credentials.secret_key_base
diff --git a/ruby-on-rails/restful-api/app/lib/message.rb b/ruby-on-rails/restful-api/app/lib/message.rb
index e47526c2..63653e18 100644
--- a/ruby-on-rails/restful-api/app/lib/message.rb
+++ b/ruby-on-rails/restful-api/app/lib/message.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class Message
   def self.not_found(record = 'record')
     "Sorry, #{record} not found."
diff --git a/ruby-on-rails/restful-api/app/mailers/application_mailer.rb b/ruby-on-rails/restful-api/app/mailers/application_mailer.rb
index 286b2239..fd2c7103 100644
--- a/ruby-on-rails/restful-api/app/mailers/application_mailer.rb
+++ b/ruby-on-rails/restful-api/app/mailers/application_mailer.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class ApplicationMailer < ActionMailer::Base
   default from: 'from@example.com'
   layout 'mailer'
diff --git a/ruby-on-rails/restful-api/app/models/application_record.rb b/ruby-on-rails/restful-api/app/models/application_record.rb
index 10a4cba8..59a2c323 100644
--- a/ruby-on-rails/restful-api/app/models/application_record.rb
+++ b/ruby-on-rails/restful-api/app/models/application_record.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class ApplicationRecord < ActiveRecord::Base
   self.abstract_class = true
 end
diff --git a/ruby-on-rails/restful-api/app/models/item.rb b/ruby-on-rails/restful-api/app/models/item.rb
index 3c718bc7..3015cce5 100644
--- a/ruby-on-rails/restful-api/app/models/item.rb
+++ b/ruby-on-rails/restful-api/app/models/item.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class Item < ApplicationRecord
   belongs_to :todo
 
diff --git a/ruby-on-rails/restful-api/app/models/todo.rb b/ruby-on-rails/restful-api/app/models/todo.rb
index d1c6048a..b7a79df1 100644
--- a/ruby-on-rails/restful-api/app/models/todo.rb
+++ b/ruby-on-rails/restful-api/app/models/todo.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class Todo < ApplicationRecord
   has_many :items, dependent: :destroy
   belongs_to :user
diff --git a/ruby-on-rails/restful-api/app/models/user.rb b/ruby-on-rails/restful-api/app/models/user.rb
index 1f43d42e..f863c1d0 100644
--- a/ruby-on-rails/restful-api/app/models/user.rb
+++ b/ruby-on-rails/restful-api/app/models/user.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class User < ApplicationRecord
   # encrypt password
   has_secure_password
diff --git a/ruby-on-rails/restful-api/app/serializers/todo_serializer.rb b/ruby-on-rails/restful-api/app/serializers/todo_serializer.rb
index ea8f839c..a581f583 100644
--- a/ruby-on-rails/restful-api/app/serializers/todo_serializer.rb
+++ b/ruby-on-rails/restful-api/app/serializers/todo_serializer.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 class TodoSerializer < ActiveModel::Serializer
   # attributes to be serialized
   attributes :id, :title, :user_id, :created_at, :updated_at
diff --git a/ruby-on-rails/restful-api/sig/generated/app/auth/authenticate_user.rbs b/ruby-on-rails/restful-api/sig/generated/app/auth/authenticate_user.rbs
new file mode 100644
index 00000000..36e6c7d7
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/auth/authenticate_user.rbs
@@ -0,0 +1,18 @@
+# Generated from app/auth/authenticate_user.rb with RBS::Inline
+
+# rbs_inline: enabled
+class AuthenticateUser
+  def initialize: (untyped email, untyped password) -> untyped
+
+  # Service entry point
+  def call: () -> untyped
+
+  private
+
+  attr_reader email: untyped
+
+  attr_reader password: untyped
+
+  # verify user credentials
+  def user: () -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/auth/authorize_api_request.rbs b/ruby-on-rails/restful-api/sig/generated/app/auth/authorize_api_request.rbs
new file mode 100644
index 00000000..42390b66
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/auth/authorize_api_request.rbs
@@ -0,0 +1,21 @@
+# Generated from app/auth/authorize_api_request.rb with RBS::Inline
+
+# rbs_inline: enabled
+class AuthorizeApiRequest
+  def initialize: (?untyped headers) -> untyped
+
+  # Service entry point - return valid user object
+  def call: () -> untyped
+
+  private
+
+  attr_reader headers: untyped
+
+  def user: () -> untyped
+
+  # decode authentication token
+  def decoded_auth_token: () -> untyped
+
+  # check for token in `Authorization` header
+  def http_auth_header: () -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/channels/application_cable/channel.rbs b/ruby-on-rails/restful-api/sig/generated/app/channels/application_cable/channel.rbs
new file mode 100644
index 00000000..e8941ece
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/channels/application_cable/channel.rbs
@@ -0,0 +1,7 @@
+# Generated from app/channels/application_cable/channel.rb with RBS::Inline
+
+# rbs_inline: enabled
+module ApplicationCable
+  class Channel < ActionCable::Channel::Base
+  end
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/channels/application_cable/connection.rbs b/ruby-on-rails/restful-api/sig/generated/app/channels/application_cable/connection.rbs
new file mode 100644
index 00000000..a8d379ac
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/channels/application_cable/connection.rbs
@@ -0,0 +1,7 @@
+# Generated from app/channels/application_cable/connection.rb with RBS::Inline
+
+# rbs_inline: enabled
+module ApplicationCable
+  class Connection < ActionCable::Connection::Base
+  end
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/controllers/application_controller.rbs b/ruby-on-rails/restful-api/sig/generated/app/controllers/application_controller.rbs
new file mode 100644
index 00000000..ea429441
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/controllers/application_controller.rbs
@@ -0,0 +1,15 @@
+# Generated from app/controllers/application_controller.rb with RBS::Inline
+
+# rbs_inline: enabled
+class ApplicationController < ActionController::API
+  include Response
+
+  include ExceptionHandler
+
+  attr_reader current_user: untyped
+
+  private
+
+  # Check for valid request token and return user
+  def authorize_request: () -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/controllers/authentication_controller.rbs b/ruby-on-rails/restful-api/sig/generated/app/controllers/authentication_controller.rbs
new file mode 100644
index 00000000..7851124d
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/controllers/authentication_controller.rbs
@@ -0,0 +1,11 @@
+# Generated from app/controllers/authentication_controller.rb with RBS::Inline
+
+# rbs_inline: enabled
+class AuthenticationController < ApplicationController
+  # return auth token once user is authenticated
+  def authenticate: () -> untyped
+
+  private
+
+  def auth_params: () -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/controllers/concerns/exception_handler.rbs b/ruby-on-rails/restful-api/sig/generated/app/controllers/concerns/exception_handler.rbs
new file mode 100644
index 00000000..bafd8f33
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/controllers/concerns/exception_handler.rbs
@@ -0,0 +1,27 @@
+# Generated from app/controllers/concerns/exception_handler.rb with RBS::Inline
+
+# rbs_inline: enabled
+module ExceptionHandler
+  extend ActiveSupport::Concern
+
+  # Define custom error subclasses - rescue catches `StandardErrors`
+  class AuthenticationError < StandardError
+  end
+
+  class MissingToken < StandardError
+  end
+
+  class InvalidToken < StandardError
+  end
+
+  private
+
+  # JSON response with message; Status code 422 - unprocessable entity
+  def four_twenty_two: (untyped error) -> untyped
+
+  # JSON response with message; Status code 401 - Unauthorized
+  def unauthorized_request: (untyped error) -> untyped
+
+  # JSON response with message; Status code 404 - NotFound
+  def four_zero_four: (untyped error) -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/controllers/concerns/response.rbs b/ruby-on-rails/restful-api/sig/generated/app/controllers/concerns/response.rbs
new file mode 100644
index 00000000..de4df6e6
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/controllers/concerns/response.rbs
@@ -0,0 +1,6 @@
+# Generated from app/controllers/concerns/response.rb with RBS::Inline
+
+# rbs_inline: enabled
+module Response
+  def json_response: (untyped object, ?untyped status) -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/controllers/users_controller.rbs b/ruby-on-rails/restful-api/sig/generated/app/controllers/users_controller.rbs
new file mode 100644
index 00000000..71688d51
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/controllers/users_controller.rbs
@@ -0,0 +1,12 @@
+# Generated from app/controllers/users_controller.rb with RBS::Inline
+
+# rbs_inline: enabled
+class UsersController < ApplicationController
+  # POST /signup
+  # return authenticated token upon signup
+  def create: () -> untyped
+
+  private
+
+  def user_params: () -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/controllers/v1/items_controller.rbs b/ruby-on-rails/restful-api/sig/generated/app/controllers/v1/items_controller.rbs
new file mode 100644
index 00000000..7d02a670
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/controllers/v1/items_controller.rbs
@@ -0,0 +1,27 @@
+# Generated from app/controllers/v1/items_controller.rb with RBS::Inline
+
+# rbs_inline: enabled
+class V1::ItemsController < ApplicationController
+  # GET /todos/:todo_id/items
+  def index: () -> untyped
+
+  # GET /todos/:todo_id/items/:id
+  def show: () -> untyped
+
+  # POST /todos/:todo_id/items
+  def create: () -> untyped
+
+  # PUT /todos/:todo_id/items/:id
+  def update: () -> untyped
+
+  # DELETE /todos/:todo_id/items/:id
+  def destroy: () -> untyped
+
+  private
+
+  def set_todo: () -> untyped
+
+  def set_todo_item: () -> untyped
+
+  def item_params: () -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/controllers/v1/todos_controller.rbs b/ruby-on-rails/restful-api/sig/generated/app/controllers/v1/todos_controller.rbs
new file mode 100644
index 00000000..93d3b834
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/controllers/v1/todos_controller.rbs
@@ -0,0 +1,25 @@
+# Generated from app/controllers/v1/todos_controller.rb with RBS::Inline
+
+# rbs_inline: enabled
+class V1::TodosController < ApplicationController
+  # GET /todos
+  def index: () -> untyped
+
+  # GET /todos/:id
+  def show: () -> untyped
+
+  # POST /todos
+  def create: () -> untyped
+
+  # PUT /todos/:id
+  def update: () -> untyped
+
+  # DELETE /todos/:id
+  def destroy: () -> untyped
+
+  private
+
+  def set_todo: () -> untyped
+
+  def todo_params: () -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/controllers/v2/todos_controller.rbs b/ruby-on-rails/restful-api/sig/generated/app/controllers/v2/todos_controller.rbs
new file mode 100644
index 00000000..71d25331
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/controllers/v2/todos_controller.rbs
@@ -0,0 +1,6 @@
+# Generated from app/controllers/v2/todos_controller.rb with RBS::Inline
+
+# rbs_inline: enabled
+class V2::TodosController < ApplicationController
+  def index: () -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/jobs/application_job.rbs b/ruby-on-rails/restful-api/sig/generated/app/jobs/application_job.rbs
new file mode 100644
index 00000000..74568208
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/jobs/application_job.rbs
@@ -0,0 +1,5 @@
+# Generated from app/jobs/application_job.rb with RBS::Inline
+
+# rbs_inline: enabled
+class ApplicationJob < ActiveJob::Base
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/lib/api_version.rbs b/ruby-on-rails/restful-api/sig/generated/app/lib/api_version.rbs
new file mode 100644
index 00000000..a3b15f94
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/lib/api_version.rbs
@@ -0,0 +1,17 @@
+# Generated from app/lib/api_version.rb with RBS::Inline
+
+# rbs_inline: enabled
+class ApiVersion
+  attr_reader version: untyped
+
+  attr_reader default: untyped
+
+  def initialize: (untyped version, ?untyped default) -> untyped
+
+  # check whether version is specified or is default
+  def matches?: (untyped request) -> untyped
+
+  private
+
+  def check_headers: (untyped headers) -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/lib/concerns/exception_handler.rbs b/ruby-on-rails/restful-api/sig/generated/app/lib/concerns/exception_handler.rbs
new file mode 100644
index 00000000..e81cf086
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/lib/concerns/exception_handler.rbs
@@ -0,0 +1,24 @@
+# Generated from app/lib/concerns/exception_handler.rb with RBS::Inline
+
+# rbs_inline: enabled
+module ExceptionHandler
+  extend ActiveSupport::Concern
+
+  # Define custom error subclasses - rescue catches `StandardErrors`
+  class AuthenticationError < StandardError
+  end
+
+  class MissingToken < StandardError
+  end
+
+  class InvalidToken < StandardError
+  end
+
+  private
+
+  # JSON response with message; Status code 422 - unprocessable entity
+  def four_twenty_two: (untyped error) -> untyped
+
+  # JSON response with message; Status code 401 - Unauthorized
+  def unauthorized_request: (untyped error) -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/lib/json_web_token.rbs b/ruby-on-rails/restful-api/sig/generated/app/lib/json_web_token.rbs
new file mode 100644
index 00000000..682a6729
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/lib/json_web_token.rbs
@@ -0,0 +1,11 @@
+# Generated from app/lib/json_web_token.rb with RBS::Inline
+
+# rbs_inline: enabled
+class JsonWebToken
+  # secret to encode and decode token
+  HMAC_SECRET: untyped
+
+  def self.encode: (untyped payload, ?untyped exp) -> untyped
+
+  def self.decode: (untyped token) -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/lib/message.rbs b/ruby-on-rails/restful-api/sig/generated/app/lib/message.rbs
new file mode 100644
index 00000000..f44d4d5f
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/lib/message.rbs
@@ -0,0 +1,20 @@
+# Generated from app/lib/message.rb with RBS::Inline
+
+# rbs_inline: enabled
+class Message
+  def self.not_found: (?untyped record) -> untyped
+
+  def self.invalid_credentials: () -> untyped
+
+  def self.invalid_token: () -> untyped
+
+  def self.missing_token: () -> untyped
+
+  def self.unauthorized: () -> untyped
+
+  def self.account_created: () -> untyped
+
+  def self.account_not_created: () -> untyped
+
+  def self.expired_token: () -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/mailers/application_mailer.rbs b/ruby-on-rails/restful-api/sig/generated/app/mailers/application_mailer.rbs
new file mode 100644
index 00000000..40a166e7
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/mailers/application_mailer.rbs
@@ -0,0 +1,5 @@
+# Generated from app/mailers/application_mailer.rb with RBS::Inline
+
+# rbs_inline: enabled
+class ApplicationMailer < ActionMailer::Base
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/models/application_record.rbs b/ruby-on-rails/restful-api/sig/generated/app/models/application_record.rbs
new file mode 100644
index 00000000..6e8c5365
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/models/application_record.rbs
@@ -0,0 +1,5 @@
+# Generated from app/models/application_record.rb with RBS::Inline
+
+# rbs_inline: enabled
+class ApplicationRecord < ActiveRecord::Base
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/models/item.rbs b/ruby-on-rails/restful-api/sig/generated/app/models/item.rbs
new file mode 100644
index 00000000..fe4c362a
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/models/item.rbs
@@ -0,0 +1,5 @@
+# Generated from app/models/item.rb with RBS::Inline
+
+# rbs_inline: enabled
+class Item < ApplicationRecord
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/models/todo.rbs b/ruby-on-rails/restful-api/sig/generated/app/models/todo.rbs
new file mode 100644
index 00000000..b5c24265
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/models/todo.rbs
@@ -0,0 +1,5 @@
+# Generated from app/models/todo.rb with RBS::Inline
+
+# rbs_inline: enabled
+class Todo < ApplicationRecord
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/models/user.rbs b/ruby-on-rails/restful-api/sig/generated/app/models/user.rbs
new file mode 100644
index 00000000..433d4e47
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/models/user.rbs
@@ -0,0 +1,5 @@
+# Generated from app/models/user.rb with RBS::Inline
+
+# rbs_inline: enabled
+class User < ApplicationRecord
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/app/serializers/todo_serializer.rbs b/ruby-on-rails/restful-api/sig/generated/app/serializers/todo_serializer.rbs
new file mode 100644
index 00000000..5e2acb66
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/app/serializers/todo_serializer.rbs
@@ -0,0 +1,5 @@
+# Generated from app/serializers/todo_serializer.rb with RBS::Inline
+
+# rbs_inline: enabled
+class TodoSerializer < ActiveModel::Serializer
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/auth/authenticate_user_spec.rbs b/ruby-on-rails/restful-api/sig/generated/spec/auth/authenticate_user_spec.rbs
new file mode 100644
index 00000000..af4967a9
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/auth/authenticate_user_spec.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/auth/authenticate_user_spec.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/auth/authorize_api_request_spec.rbs b/ruby-on-rails/restful-api/sig/generated/spec/auth/authorize_api_request_spec.rbs
new file mode 100644
index 00000000..da659c50
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/auth/authorize_api_request_spec.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/auth/authorize_api_request_spec.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/controllers/application_controller_spec.rbs b/ruby-on-rails/restful-api/sig/generated/spec/controllers/application_controller_spec.rbs
new file mode 100644
index 00000000..05966158
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/controllers/application_controller_spec.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/controllers/application_controller_spec.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/factories/items.rbs b/ruby-on-rails/restful-api/sig/generated/spec/factories/items.rbs
new file mode 100644
index 00000000..0e6c39f5
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/factories/items.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/factories/items.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/factories/todos.rbs b/ruby-on-rails/restful-api/sig/generated/spec/factories/todos.rbs
new file mode 100644
index 00000000..c62c67ea
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/factories/todos.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/factories/todos.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/factories/user.rbs b/ruby-on-rails/restful-api/sig/generated/spec/factories/user.rbs
new file mode 100644
index 00000000..22e0ea7a
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/factories/user.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/factories/user.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/models/item_spec.rbs b/ruby-on-rails/restful-api/sig/generated/spec/models/item_spec.rbs
new file mode 100644
index 00000000..d58b6381
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/models/item_spec.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/models/item_spec.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/models/todo_spec.rbs b/ruby-on-rails/restful-api/sig/generated/spec/models/todo_spec.rbs
new file mode 100644
index 00000000..0a39eb8d
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/models/todo_spec.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/models/todo_spec.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/models/user_spec.rbs b/ruby-on-rails/restful-api/sig/generated/spec/models/user_spec.rbs
new file mode 100644
index 00000000..f63e81a3
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/models/user_spec.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/models/user_spec.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/rails_helper.rbs b/ruby-on-rails/restful-api/sig/generated/spec/rails_helper.rbs
new file mode 100644
index 00000000..47c0332c
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/rails_helper.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/rails_helper.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/requests/authentication_spec.rbs b/ruby-on-rails/restful-api/sig/generated/spec/requests/authentication_spec.rbs
new file mode 100644
index 00000000..5f48d9b6
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/requests/authentication_spec.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/requests/authentication_spec.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/requests/items_spec.rbs b/ruby-on-rails/restful-api/sig/generated/spec/requests/items_spec.rbs
new file mode 100644
index 00000000..d1f6e934
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/requests/items_spec.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/requests/items_spec.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/requests/todos_spec.rbs b/ruby-on-rails/restful-api/sig/generated/spec/requests/todos_spec.rbs
new file mode 100644
index 00000000..787eac37
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/requests/todos_spec.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/requests/todos_spec.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/requests/users_spec.rbs b/ruby-on-rails/restful-api/sig/generated/spec/requests/users_spec.rbs
new file mode 100644
index 00000000..e83f64b2
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/requests/users_spec.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/requests/users_spec.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/spec_helper.rbs b/ruby-on-rails/restful-api/sig/generated/spec/spec_helper.rbs
new file mode 100644
index 00000000..5af4f2a5
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/spec_helper.rbs
@@ -0,0 +1,2 @@
+# Generated from spec/spec_helper.rb with RBS::Inline
+
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/support/controller_spec_helper.rbs b/ruby-on-rails/restful-api/sig/generated/spec/support/controller_spec_helper.rbs
new file mode 100644
index 00000000..3649112f
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/support/controller_spec_helper.rbs
@@ -0,0 +1,16 @@
+# Generated from spec/support/controller_spec_helper.rb with RBS::Inline
+
+# rbs_inline: enabled
+module ControllerSpecHelper
+  # generate tokens from user id
+  def token_generator: (untyped user_id) -> untyped
+
+  # generate expired tokens from user id
+  def expired_token_generator: (untyped user_id) -> untyped
+
+  # return valid headers
+  def valid_headers: (?untyped version) -> untyped
+
+  # return invalid headers
+  def invalid_headers: (?untyped version) -> untyped
+end
diff --git a/ruby-on-rails/restful-api/sig/generated/spec/support/request_spec_helper.rbs b/ruby-on-rails/restful-api/sig/generated/spec/support/request_spec_helper.rbs
new file mode 100644
index 00000000..1a669dee
--- /dev/null
+++ b/ruby-on-rails/restful-api/sig/generated/spec/support/request_spec_helper.rbs
@@ -0,0 +1,7 @@
+# Generated from spec/support/request_spec_helper.rb with RBS::Inline
+
+# rbs_inline: enabled
+module RequestSpecHelper
+  # Parse JSON response to ruby hash
+  def json: () -> untyped
+end
diff --git a/ruby-on-rails/restful-api/spec/auth/authenticate_user_spec.rb b/ruby-on-rails/restful-api/spec/auth/authenticate_user_spec.rb
index 5c74f6bf..590fb922 100644
--- a/ruby-on-rails/restful-api/spec/auth/authenticate_user_spec.rb
+++ b/ruby-on-rails/restful-api/spec/auth/authenticate_user_spec.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 require 'rails_helper'
 
 RSpec.describe AuthenticateUser do
diff --git a/ruby-on-rails/restful-api/spec/auth/authorize_api_request_spec.rb b/ruby-on-rails/restful-api/spec/auth/authorize_api_request_spec.rb
index 3eccaa73..4d838577 100644
--- a/ruby-on-rails/restful-api/spec/auth/authorize_api_request_spec.rb
+++ b/ruby-on-rails/restful-api/spec/auth/authorize_api_request_spec.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 require 'rails_helper'
 
 RSpec.describe AuthorizeApiRequest do
diff --git a/ruby-on-rails/restful-api/spec/controllers/application_controller_spec.rb b/ruby-on-rails/restful-api/spec/controllers/application_controller_spec.rb
index d31dda1f..c2e6e398 100644
--- a/ruby-on-rails/restful-api/spec/controllers/application_controller_spec.rb
+++ b/ruby-on-rails/restful-api/spec/controllers/application_controller_spec.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 require 'rails_helper'
 
 RSpec.describe ApplicationController, type: :controller do
diff --git a/ruby-on-rails/restful-api/spec/factories/items.rb b/ruby-on-rails/restful-api/spec/factories/items.rb
index 41ef2a6c..5da3c750 100644
--- a/ruby-on-rails/restful-api/spec/factories/items.rb
+++ b/ruby-on-rails/restful-api/spec/factories/items.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 FactoryBot.define do
   factory :item do
     name { Faker::Lorem.word }
diff --git a/ruby-on-rails/restful-api/spec/factories/todos.rb b/ruby-on-rails/restful-api/spec/factories/todos.rb
index 4d595381..2948729a 100644
--- a/ruby-on-rails/restful-api/spec/factories/todos.rb
+++ b/ruby-on-rails/restful-api/spec/factories/todos.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 FactoryBot.define do
   factory :todo do
     title { Faker::Lorem.word }
diff --git a/ruby-on-rails/restful-api/spec/factories/user.rb b/ruby-on-rails/restful-api/spec/factories/user.rb
index 6d11300b..769ad68c 100644
--- a/ruby-on-rails/restful-api/spec/factories/user.rb
+++ b/ruby-on-rails/restful-api/spec/factories/user.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 FactoryBot.define do
   factory :user do
     name { Faker::Name.name }
diff --git a/ruby-on-rails/restful-api/spec/models/item_spec.rb b/ruby-on-rails/restful-api/spec/models/item_spec.rb
index 41338d2a..672d4428 100644
--- a/ruby-on-rails/restful-api/spec/models/item_spec.rb
+++ b/ruby-on-rails/restful-api/spec/models/item_spec.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 require 'rails_helper'
 
 # Test suite for the Item model
diff --git a/ruby-on-rails/restful-api/spec/models/todo_spec.rb b/ruby-on-rails/restful-api/spec/models/todo_spec.rb
index 1d56b1f4..1a0ef2cf 100644
--- a/ruby-on-rails/restful-api/spec/models/todo_spec.rb
+++ b/ruby-on-rails/restful-api/spec/models/todo_spec.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 require 'rails_helper'
 
 # Test suite for the Todo model
diff --git a/ruby-on-rails/restful-api/spec/models/user_spec.rb b/ruby-on-rails/restful-api/spec/models/user_spec.rb
index cd44a29a..aabf1b4e 100644
--- a/ruby-on-rails/restful-api/spec/models/user_spec.rb
+++ b/ruby-on-rails/restful-api/spec/models/user_spec.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 require 'rails_helper'
 
 # Test suite for User model
diff --git a/ruby-on-rails/restful-api/spec/rails_helper.rb b/ruby-on-rails/restful-api/spec/rails_helper.rb
index b962b7c4..43615779 100644
--- a/ruby-on-rails/restful-api/spec/rails_helper.rb
+++ b/ruby-on-rails/restful-api/spec/rails_helper.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 # This file is copied to spec/ when you run 'rails generate rspec:install'
 require 'spec_helper'
 ENV['RAILS_ENV'] ||= 'test'
diff --git a/ruby-on-rails/restful-api/spec/requests/authentication_spec.rb b/ruby-on-rails/restful-api/spec/requests/authentication_spec.rb
index 1fe3e3f0..a81f1aa2 100644
--- a/ruby-on-rails/restful-api/spec/requests/authentication_spec.rb
+++ b/ruby-on-rails/restful-api/spec/requests/authentication_spec.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 require 'rails_helper'
 
 RSpec.describe 'Authentication', type: :request do
diff --git a/ruby-on-rails/restful-api/spec/requests/items_spec.rb b/ruby-on-rails/restful-api/spec/requests/items_spec.rb
index 60cbcb69..178c4e12 100644
--- a/ruby-on-rails/restful-api/spec/requests/items_spec.rb
+++ b/ruby-on-rails/restful-api/spec/requests/items_spec.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 require 'rails_helper'
 
 RSpec.describe 'Items API' do
diff --git a/ruby-on-rails/restful-api/spec/requests/todos_spec.rb b/ruby-on-rails/restful-api/spec/requests/todos_spec.rb
index 62e2bcaf..f153da2d 100644
--- a/ruby-on-rails/restful-api/spec/requests/todos_spec.rb
+++ b/ruby-on-rails/restful-api/spec/requests/todos_spec.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 require 'rails_helper'
 
 RSpec.describe 'Todos API', type: :request do
diff --git a/ruby-on-rails/restful-api/spec/requests/users_spec.rb b/ruby-on-rails/restful-api/spec/requests/users_spec.rb
index 7cf844b2..57828462 100644
--- a/ruby-on-rails/restful-api/spec/requests/users_spec.rb
+++ b/ruby-on-rails/restful-api/spec/requests/users_spec.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 require 'rails_helper'
 
 RSpec.describe 'Users API', type: :request do
diff --git a/ruby-on-rails/restful-api/spec/spec_helper.rb b/ruby-on-rails/restful-api/spec/spec_helper.rb
index ce33d66d..09c4d07d 100644
--- a/ruby-on-rails/restful-api/spec/spec_helper.rb
+++ b/ruby-on-rails/restful-api/spec/spec_helper.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 # This file was generated by the `rails generate rspec:install` command. Conventionally, all
 # specs live under a `spec` directory, which RSpec adds to the `$LOAD_PATH`.
 # The generated `.rspec` file contains `--require spec_helper` which will cause
diff --git a/ruby-on-rails/restful-api/spec/support/controller_spec_helper.rb b/ruby-on-rails/restful-api/spec/support/controller_spec_helper.rb
index a1be9de5..51aafc8d 100644
--- a/ruby-on-rails/restful-api/spec/support/controller_spec_helper.rb
+++ b/ruby-on-rails/restful-api/spec/support/controller_spec_helper.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 module ControllerSpecHelper
   # generate tokens from user id
   def token_generator(user_id)
diff --git a/ruby-on-rails/restful-api/spec/support/request_spec_helper.rb b/ruby-on-rails/restful-api/spec/support/request_spec_helper.rb
index 4c2b8ad0..d573d8ee 100644
--- a/ruby-on-rails/restful-api/spec/support/request_spec_helper.rb
+++ b/ruby-on-rails/restful-api/spec/support/request_spec_helper.rb
@@ -1,3 +1,4 @@
+# rbs_inline: enabled
 module RequestSpecHelper
   # Parse JSON response to ruby hash
   def json