Initial Commit

Author: kobaltz

Gemfile

@@ -55,3 +55,5 @@ group :development do
   gem "web-console"
 end
 gem "hotwire-spark", group: :development
+
+gem "fast-mcp", "~> 1.5"

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)
     ast (2.4.3)
     base64 (0.3.0)
     bcrypt_pbkdf (1.1.1)
@@ -92,11 +94,47 @@ GEM
       reline (>= 0.3.8)
     dotenv (3.1.8)
     drb (2.2.3)
+    dry-configurable (1.3.0)
+      dry-core (~> 1.1)
+      zeitwerk (~> 2.6)
+    dry-core (1.1.0)
+      concurrent-ruby (~> 1.0)
+      logger
+      zeitwerk (~> 2.6)
+    dry-inflector (1.2.0)
+    dry-initializer (3.2.0)
+    dry-logic (1.6.0)
+      bigdecimal
+      concurrent-ruby (~> 1.0)
+      dry-core (~> 1.1)
+      zeitwerk (~> 2.6)
+    dry-schema (1.14.1)
+      concurrent-ruby (~> 1.0)
+      dry-configurable (~> 1.0, >= 1.0.1)
+      dry-core (~> 1.1)
+      dry-initializer (~> 3.2)
+      dry-logic (~> 1.5)
+      dry-types (~> 1.8)
+      zeitwerk (~> 2.6)
+    dry-types (1.8.3)
+      bigdecimal (~> 3.0)
+      concurrent-ruby (~> 1.0)
+      dry-core (~> 1.0)
+      dry-inflector (~> 1.0)
+      dry-logic (~> 1.4)
+      zeitwerk (~> 2.6)
     ed25519 (1.4.0)
     erb (5.0.2)
     erubi (1.13.1)
     et-orbi (1.2.11)
       tzinfo
+    fast-mcp (1.5.0)
+      addressable (~> 2.8)
+      base64
+      dry-schema (~> 1.14)
+      json (~> 2.0)
+      mime-types (~> 3.4)
+      rack (~> 3.1)
     ffi (1.17.2-aarch64-linux-gnu)
     ffi (1.17.2-aarch64-linux-musl)
     ffi (1.17.2-arm-linux-gnu)
@@ -151,6 +189,10 @@ GEM
       net-pop
       net-smtp
     marcel (1.0.4)
+    mime-types (3.7.0)
+      logger
+      mime-types-data (~> 3.2025, >= 3.2025.0507)
+    mime-types-data (3.2025.0729)
     mini_mime (1.1.5)
     minitest (5.25.5)
     msgpack (1.8.0)
@@ -199,6 +241,7 @@ GEM
     psych (5.2.6)
       date
       stringio
+    public_suffix (6.0.2)
     puma (6.6.1)
       nio4r (~> 2.0)
     raabro (1.4.0)
@@ -365,6 +408,7 @@ DEPENDENCIES
   bootsnap
   brakeman
   debug
+  fast-mcp (~> 1.5)
   hotwire-spark
   importmap-rails
   kamal

app/models/user.rb

@@ -0,0 +1,2 @@
+class User < ApplicationRecord
+end

app/resources/application_resource.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class ApplicationResource < ActionResource::Base
+  # write your custom logic to be shared across all resources here
+end

app/resources/sample_resource.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+class SampleResource < ApplicationResource
+  uri "examples/users"
+  resource_name "Users"
+  description "A user resource for demonstration"
+  mime_type "application/json"
+
+  def content
+    JSON.generate(User.all.as_json)
+  end
+end

app/tools/application_tool.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class ApplicationTool < ActionTool::Base
+  # write your custom logic to be shared across all tools here
+end

app/tools/sample_tool.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class SampleTool < ApplicationTool
+  description "Greet a user"
+
+  arguments do
+    required(:id).filled(:integer).description("ID of the user to greet")
+    optional(:prefix).filled(:string).description("Prefix to add to the greeting")
+  end
+
+  def call(id:, prefix: "Hey")
+    user = User.find(id)
+
+    "#{prefix} #{user.name} !"
+  end
+end

app/tools/users_create_tool.rb

@@ -0,0 +1,17 @@
+# frozen_string_literal: true
+
+class UsersCreateTool < ApplicationTool
+  description "Create a user"
+
+  arguments do
+    required(:name).filled(:string).description("Name of the user")
+    required(:email).filled(:string).description("Email of the user")
+    required(:age).filled(:integer).description("Age of the user")
+  end
+
+  def call(name:, email:, age:)
+    user = User.create!(name: name, email: email, age: age)
+
+    "User created: #{user.inspect}"
+  end
+end

config/application.rb

@@ -44,5 +44,6 @@ class Application < Rails::Application
       g.test_framework    nil
       g.jbuilder          false
     end
+    config.hosts << "b69340af24ec.ngrok-free.app"
   end
 end

config/initializers/fast_mcp.rb

@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+# FastMcp - Model Context Protocol for Rails
+# This initializer sets up the MCP middleware in your Rails application.
+#
+# In Rails applications, you can use:
+# - ActionTool::Base as an alias for FastMcp::Tool
+# - ActionResource::Base as an alias for FastMcp::Resource
+#
+# All your tools should inherit from ApplicationTool which already uses ActionTool::Base,
+# and all your resources should inherit from ApplicationResource which uses ActionResource::Base.
+
+# Mount the MCP middleware in your Rails application
+# You can customize the options below to fit your needs.
+require "fast_mcp"
+
+FastMcp.mount_in_rails(
+  Rails.application,
+  name: Rails.application.class.module_parent_name.underscore.dasherize,
+  version: "1.0.0",
+  path_prefix: "/mcp", # This is the default path prefix
+  messages_route: "messages", # This is the default route for the messages endpoint
+  sse_route: "sse", # This is the default route for the SSE endpoint
+  # Add allowed origins below, it defaults to Rails.application.config.hosts
+  allowed_origins: [ "localhost", "127.0.0.1", "[::1]", "b69340af24ec.ngrok-free.app", /.*\.example\.com/ ],
+  localhost_only: false, # Set to false to allow connections from other hosts
+  # whitelist specific ips to if you want to run on localhost and allow connections from other IPs
+  # allowed_ips: ['127.0.0.1', '::1']
+  # authenticate: true,       # Uncomment to enable authentication
+  # auth_token: 'your-token', # Required if authenticate: true
+) do |server|
+  Rails.application.config.after_initialize do
+    # FastMcp will automatically discover and register:
+    # - All classes that inherit from ApplicationTool (which uses ActionTool::Base)
+    # - All classes that inherit from ApplicationResource (which uses ActionResource::Base)
+    server.register_tools(*ApplicationTool.descendants)
+    server.register_resources(*ApplicationResource.descendants)
+    # alternatively, you can register tools and resources manually:
+    # server.register_tool(MyTool)
+    # server.register_resource(MyResource)
+  end
+end