diff --git a/.devcontainer/devcontainer.json b/.devcontainer/devcontainer.json
index 614dc3c..2cc905a 100644
--- a/.devcontainer/devcontainer.json
+++ b/.devcontainer/devcontainer.json
@@ -39,6 +39,7 @@
   // Mount host's ~/.claude if it exists
   "mounts": [
     "source=${localEnv:HOME}/.claude,target=/home/vscode/.claude,type=bind,consistency=cached",
-    "source=${localEnv:HOME}/.claude.json,target=/home/vscode/.claude.json,type=bind,consistency=cached"
+    "source=${localEnv:HOME}/.claude.json,target=/home/vscode/.claude.json,type=bind,consistency=cached",
+    "source=${localEnv:HOME}/.mcp.json,target=/home/vscode/.mcp.json,type=bind,consistency=cached"
   ]
 }
diff --git a/.mcp.json b/.mcp.json
new file mode 100644
index 0000000..c509dd4
--- /dev/null
+++ b/.mcp.json
@@ -0,0 +1,5 @@
+{
+  "mcpServers": {
+    "spotlight-rails": {}
+  }
+}
\ No newline at end of file
diff --git a/Gemfile b/Gemfile
index 10e3f82..6ca5bc7 100644
--- a/Gemfile
+++ b/Gemfile
@@ -75,3 +75,6 @@ gem "metainspector", "~> 5.15"
 gem "rswag-api"
 gem "rswag-ui"
 gem "rswag-specs", group: [ :development, :test ]
+
+# Model Context Protocol (MCP) for LLM integration
+gem "mcp"
diff --git a/Gemfile.lock b/Gemfile.lock
index 4490a7a..a4e8821 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -75,10 +75,10 @@ GEM
     addressable (2.8.7)
       public_suffix (>= 2.0.2, < 7.0)
     ast (2.4.2)
-    base64 (0.2.0)
+    base64 (0.3.0)
     bcrypt_pbkdf (1.1.1)
-    benchmark (0.4.0)
-    bigdecimal (3.1.9)
+    benchmark (0.4.1)
+    bigdecimal (3.2.2)
     bindex (0.8.1)
     bootsnap (1.18.4)
       msgpack (~> 1.2)
@@ -86,7 +86,7 @@ GEM
       racc
     builder (3.3.0)
     concurrent-ruby (1.3.5)
-    connection_pool (2.5.0)
+    connection_pool (2.5.3)
     crass (1.0.6)
     date (3.4.1)
     debug (1.10.0)
@@ -94,9 +94,9 @@ GEM
       reline (>= 0.3.8)
     diff-lcs (1.6.1)
     domain_name (0.6.20240107)
-    dotenv (3.1.7)
-    drb (2.2.1)
-    ed25519 (1.3.0)
+    dotenv (3.1.8)
+    drb (2.2.3)
+    ed25519 (1.4.0)
     erubi (1.13.1)
     et-orbi (1.2.11)
       tzinfo
@@ -163,20 +163,21 @@ GEM
     json-schema (5.1.1)
       addressable (~> 2.8)
       bigdecimal (~> 3.1)
-    kamal (2.5.2)
+    json_rpc_handler (0.1.1)
+    kamal (2.7.0)
       activesupport (>= 7.0)
       base64 (~> 0.2)
       bcrypt_pbkdf (~> 1.0)
       concurrent-ruby (~> 1.2)
       dotenv (~> 3.1)
-      ed25519 (~> 1.2)
+      ed25519 (~> 1.4)
       net-ssh (~> 7.3)
       sshkit (>= 1.23.0, < 2.0)
       thor (~> 1.3)
       zeitwerk (>= 2.6.18, < 3.0)
     language_server-protocol (3.17.0.4)
     lint_roller (1.1.0)
-    logger (1.6.6)
+    logger (1.7.0)
     loofah (2.24.0)
       crass (~> 1.0.2)
       nokogiri (>= 1.12.0)
@@ -186,6 +187,8 @@ GEM
       net-pop
       net-smtp
     marcel (1.0.4)
+    mcp (0.1.0)
+      json_rpc_handler (~> 0.1)
     metainspector (5.15.0)
       addressable (~> 2.8.4)
       faraday (~> 2.5)
@@ -203,7 +206,7 @@ GEM
       benchmark
       logger
     mini_mime (1.1.5)
-    minitest (5.25.4)
+    minitest (5.25.5)
     msgpack (1.8.0)
     nesty (1.0.2)
     net-http (0.6.0)
@@ -235,7 +238,7 @@ GEM
       racc (~> 1.4)
     nokogiri (1.18.3-x86_64-linux-musl)
       racc (~> 1.4)
-    ostruct (0.6.1)
+    ostruct (0.6.2)
     parallel (1.26.3)
     parser (3.3.7.1)
       ast (~> 2.4.1)
@@ -419,7 +422,7 @@ GEM
     unicode-display_width (3.1.4)
       unicode-emoji (~> 4.0, >= 4.0.4)
     unicode-emoji (4.0.4)
-    uri (1.0.2)
+    uri (1.0.3)
     useragent (0.16.11)
     view_component (3.21.0)
       activesupport (>= 5.2.0, < 8.1)
@@ -434,7 +437,7 @@ GEM
       base64
       websocket-extensions (>= 0.1.0)
     websocket-extensions (0.1.5)
-    zeitwerk (2.7.2)
+    zeitwerk (2.7.3)
     zlib (2.1.1)
 
 PLATFORMS
@@ -457,6 +460,7 @@ DEPENDENCIES
   importmap-rails
   jbuilder
   kamal
+  mcp
   metainspector (~> 5.15)
   propshaft
   puma (>= 5.0)
diff --git a/README.md b/README.md
index b852569..64cdb26 100644
--- a/README.md
+++ b/README.md
@@ -41,3 +41,21 @@ bundle exec rails rswag:specs:swaggerize
 ```
 
 http://localhost:3000/api-docs/
+
+## MCP サーバー
+記事の更新のためのMCPサーバーを実装しています。
+
+```json:~/.mcp.json
+{
+  "mcpServers": {
+    "spotlight-rails": {
+      "type": "http",
+      "url": "https://takeyuweb.co.jp/api/mcp",
+      "method": "POST",
+      "headers": {
+        "Authorization": "Bearer token"
+      }
+    }
+  }
+}
+```
diff --git a/app/controllers/api/mcp_controller.rb b/app/controllers/api/mcp_controller.rb
new file mode 100644
index 0000000..e080a89
--- /dev/null
+++ b/app/controllers/api/mcp_controller.rb
@@ -0,0 +1,51 @@
+# frozen_string_literal: true
+
+module Api
+  class McpController < ApplicationController
+    skip_before_action :verify_authenticity_token
+    before_action :authenticate_mcp_request
+
+    def handle
+      # Create MCP server instance
+      server = ArticleServer.create
+
+      # Handle the JSON-RPC request
+      response = server.handle_json(request.raw_post)
+
+      # Return response
+      render json: response
+    rescue => e
+      Rails.logger.error "MCP Error: #{e.message}"
+      Rails.logger.error e.backtrace.join("\n")
+
+      render json: {
+        jsonrpc: "2.0",
+        error: {
+          code: -32603,
+          message: "Internal error",
+          data: { details: e.message }
+        },
+        id: nil
+      }, status: :internal_server_error
+    end
+
+    private
+
+    def authenticate_mcp_request
+      token = request.headers["Authorization"]&.gsub(/^Bearer\s+/, "")
+      expected_token = Rails.application.credentials.dig(:mcp, :api_token)
+
+      unless token.present? && ActiveSupport::SecurityUtils.secure_compare(token, expected_token)
+        render json: {
+          jsonrpc: "2.0",
+          error: {
+            code: -32603,
+            message: "Unauthorized",
+            data: { details: "Invalid or missing authentication token" }
+          },
+          id: params[:id]
+        }, status: :unauthorized
+      end
+    end
+  end
+end
diff --git a/app/mcp/article_server.rb b/app/mcp/article_server.rb
new file mode 100644
index 0000000..a2b212e
--- /dev/null
+++ b/app/mcp/article_server.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class ArticleServer
+  def self.create
+    MCP::Server.new(
+      name: "spotlight-rails-articles",
+      version: "1.0.0",
+      tools: [
+        Tools::CreateArticleTool,
+        Tools::UpdateArticleTool,
+        Tools::FindArticleTool
+      ],
+      server_context: {}
+    )
+  end
+end
diff --git a/app/mcp/tools/create_article_tool.rb b/app/mcp/tools/create_article_tool.rb
new file mode 100644
index 0000000..e211b56
--- /dev/null
+++ b/app/mcp/tools/create_article_tool.rb
@@ -0,0 +1,42 @@
+# frozen_string_literal: true
+
+module Tools
+  class CreateArticleTool < MCP::Tool
+    description "Create a new article from markdown content with YAML frontmatter"
+
+    input_schema(
+      properties: {
+        content: {
+          type: "string",
+          description: "The markdown content with YAML frontmatter (including title, slug, description, published_date, tags, etc.)"
+        }
+      },
+      required: [ "content" ]
+    )
+
+    def self.call(content:, server_context:)
+      article = Article.import_from_markdown(content)
+
+      if article
+        MCP::Tool::Response.new([ {
+          type: "text",
+          text: "Article created successfully:\n" \
+                "- Title: #{article.title}\n" \
+                "- Slug: #{article.slug}\n" \
+                "- Published at: #{article.published_at}\n" \
+                "- Tags: #{article.tags.pluck(:name).join(', ')}"
+        } ])
+      else
+        MCP::Tool::Response.new([ {
+          type: "text",
+          text: "Failed to create article. Please check the markdown content and ensure it has valid YAML frontmatter with required fields (title, slug, description, published_date)."
+        } ])
+      end
+    rescue => e
+      MCP::Tool::Response.new([ {
+        type: "text",
+        text: "Error creating article: #{e.message}"
+      } ])
+    end
+  end
+end
diff --git a/app/mcp/tools/find_article_tool.rb b/app/mcp/tools/find_article_tool.rb
new file mode 100644
index 0000000..e76436c
--- /dev/null
+++ b/app/mcp/tools/find_article_tool.rb
@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module Tools
+  class FindArticleTool < MCP::Tool
+    description "Find an article by slug and return its details"
+
+    input_schema(
+      properties: {
+        slug: {
+          type: "string",
+          description: "The slug of the article to find"
+        }
+      },
+      required: [ "slug" ]
+    )
+
+    def self.call(slug:, server_context:)
+      article = Article.find_by(slug: slug)
+
+      if article
+        MCP::Tool::Response.new([ {
+          type: "text",
+          text: "Article found:\n" \
+                "- Title: #{article.title}\n" \
+                "- Slug: #{article.slug}\n" \
+                "- Description: #{article.description}\n" \
+                "- Published at: #{article.published_at}\n" \
+                "- Tags: #{article.tags.pluck(:name).join(', ')}\n" \
+                "- Created at: #{article.created_at}\n" \
+                "- Updated at: #{article.updated_at}"
+        } ])
+      else
+        MCP::Tool::Response.new([ {
+          type: "text",
+          text: "Article not found with slug: #{slug}"
+        } ])
+      end
+    rescue => e
+      MCP::Tool::Response.new([ {
+        type: "text",
+        text: "Error finding article: #{e.message}"
+      } ])
+    end
+  end
+end
diff --git a/app/mcp/tools/update_article_tool.rb b/app/mcp/tools/update_article_tool.rb
new file mode 100644
index 0000000..4eebdb9
--- /dev/null
+++ b/app/mcp/tools/update_article_tool.rb
@@ -0,0 +1,57 @@
+# frozen_string_literal: true
+
+module Tools
+  class UpdateArticleTool < MCP::Tool
+    description "Update an existing article by slug with new markdown content"
+
+    input_schema(
+      properties: {
+        slug: {
+          type: "string",
+          description: "The slug of the article to update"
+        },
+        content: {
+          type: "string",
+          description: "The new markdown content with YAML frontmatter"
+        }
+      },
+      required: [ "slug", "content" ]
+    )
+
+    def self.call(slug:, content:, server_context:)
+      # Find the existing article
+      article = Article.find_by(slug: slug)
+
+      unless article
+        return MCP::Tool::Response.new([ {
+          type: "text",
+          text: "Article not found with slug: #{slug}"
+        } ])
+      end
+
+      # Update the article with new content
+      updated_article = Article.import_from_markdown(content)
+
+      if updated_article
+        MCP::Tool::Response.new([ {
+          type: "text",
+          text: "Article updated successfully:\n" \
+                "- Title: #{updated_article.title}\n" \
+                "- Slug: #{updated_article.slug}\n" \
+                "- Published at: #{updated_article.published_at}\n" \
+                "- Tags: #{updated_article.tags.pluck(:name).join(', ')}"
+        } ])
+      else
+        MCP::Tool::Response.new([ {
+          type: "text",
+          text: "Failed to update article. Please check the markdown content and ensure it has valid YAML frontmatter."
+        } ])
+      end
+    rescue => e
+      MCP::Tool::Response.new([ {
+        type: "text",
+        text: "Error updating article: #{e.message}"
+      } ])
+    end
+  end
+end
diff --git a/app/models/article.rb b/app/models/article.rb
index 9d59a08..bc0af48 100644
--- a/app/models/article.rb
+++ b/app/models/article.rb
@@ -15,10 +15,10 @@ def to_param
     slug
   end
 
-  # Import articles from markdown files
-  # @param source_dir [String] Path to the directory containing article markdown files
-  # @return [Integer] Number of articles imported
-  def self.import_from_docs(source_dir)
+  # Import a single article from markdown content
+  # @param markdown_content [String] The markdown content with YAML frontmatter
+  # @return [Article, nil] The created/updated article, or nil if failed
+  def self.import_from_markdown(markdown_content)
     require "redcarpet"
 
     # Initialize Markdown renderer with custom renderer for special syntax
@@ -34,60 +34,75 @@ def self.import_from_docs(source_dir)
       quote: true
     })
 
+    # Parse metadata using MetadataParser service
+    parsed_data = MetadataParser.parse(markdown_content)
+    metadata = parsed_data[:metadata]
+    content = parsed_data[:content]
+
+    # Only process articles
+    return nil unless metadata[:category] == "article"
+
+    # Convert markdown to HTML
+    html_content = markdown.render(content)
+
+    # Find or create article by slug
+    article = find_or_initialize_by(slug: metadata[:slug])
+
+    # Update article attributes from parsed metadata
+    article.title = metadata[:title]
+    article.description = metadata[:description]
+    article.published_at = metadata[:published_date]
+    article.content = html_content
+
+    # Save the article
+    if article.save
+      # Process tags if present
+      if metadata[:tags]
+        article.tags.clear # Remove existing tags
+
+        metadata[:tags].each do |tag_name|
+          next if tag_name.blank?
+
+          tag = Tag.find_or_create_by(name: tag_name)
+          article.tags << tag unless article.tags.include?(tag)
+        end
+      end
+
+      article
+    else
+      Rails.logger.error "Error saving article: #{article.errors.full_messages.join(', ')}"
+      nil
+    end
+  rescue MetadataParser::MetadataParseError => e
+    Rails.logger.error "Metadata parsing error: #{e.message}"
+    nil
+  rescue => e
+    Rails.logger.error "Error processing article: #{e.message}"
+    nil
+  end
+
+  # Import articles from markdown files
+  # @param source_dir [String] Path to the directory containing article markdown files
+  # @return [Integer] Number of articles imported
+  def self.import_from_docs(source_dir)
     # Find all markdown files in the source directory
     article_files = Dir.glob(File.join(source_dir, "**", "*.md"))
 
     imported_count = 0
     article_files.each do |file_path|
-      begin
-        puts "Processing article: #{file_path}"
-
-        # Read the file content
-        file_content = File.read(file_path)
-
-        # Parse metadata using MetadataParser service
-        parsed_data = MetadataParser.parse(file_content)
-        metadata = parsed_data[:metadata]
-        markdown_content = parsed_data[:content]
-
-        # Skip if not an article
-        next unless metadata[:category] == "article"
-
-        # Convert markdown to HTML
-        html_content = markdown.render(markdown_content)
-
-        # Find or create article by slug
-        article = find_or_initialize_by(slug: metadata[:slug])
-
-        # Update article attributes from parsed metadata
-        article.title = metadata[:title]
-        article.description = metadata[:description]
-        article.published_at = metadata[:published_date]
-        article.content = html_content
-
-        # Save the article
-        if article.save
-          # Process tags if present
-          if metadata[:tags]
-            article.tags.clear # Remove existing tags
-
-            metadata[:tags].each do |tag_name|
-              next if tag_name.blank?
-
-              tag = Tag.find_or_create_by(name: tag_name)
-              article.tags << tag unless article.tags.include?(tag)
-            end
-          end
-
-          puts "  Saved article: #{article.title}"
-          imported_count += 1
-        else
-          puts "  Error saving article: #{article.errors.full_messages.join(', ')}"
-        end
-      rescue MetadataParser::MetadataParseError => e
-        puts "  Metadata parsing error for #{file_path}: #{e.message}"
-      rescue => e
-        puts "  Error processing article #{file_path}: #{e.message}"
+      puts "Processing article: #{file_path}"
+
+      # Read the file content
+      file_content = File.read(file_path)
+
+      # Import the article from markdown content
+      article = import_from_markdown(file_content)
+
+      if article
+        puts "  Saved article: #{article.title}"
+        imported_count += 1
+      else
+        puts "  Failed to import article from #{file_path}"
       end
     end
 
diff --git a/config/credentials.yml.enc b/config/credentials.yml.enc
index b9c9453..e57c020 100644
--- a/config/credentials.yml.enc
+++ b/config/credentials.yml.enc
@@ -1 +1 @@
-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--/6H6KbJ8Pqm5ML3Q--3VoTdSjm9dagLNK0v1bUuw==
\ No newline at end of file
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--70ibUpgcNuA7ZOM9--JCSrfQ+x80/ucEXXSzUPqA==
\ No newline at end of file
diff --git a/config/routes.rb b/config/routes.rb
index 990fbba..cee1160 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -30,6 +30,9 @@
         get :metadata
       end
     end
+
+    # MCP endpoint for article management
+    post "mcp", to: "mcp#handle"
   end
 
   # Render dynamic PWA files from app/views/pwa/* (remember to link manifest in application.html.erb)
diff --git a/spec/requests/api/mcp_spec.rb b/spec/requests/api/mcp_spec.rb
new file mode 100644
index 0000000..6ee367c
--- /dev/null
+++ b/spec/requests/api/mcp_spec.rb
@@ -0,0 +1,206 @@
+require 'rails_helper'
+
+RSpec.describe "Api::Mcp", type: :request do
+  describe "POST /api/mcp" do
+    let(:valid_token) { Rails.application.credentials.dig(:mcp, :api_token) }
+    let(:headers) { { "Authorization" => "Bearer #{valid_token}", "Content-Type" => "application/json" } }
+
+    context "with valid authentication" do
+      context "when handling server info request" do
+        let(:request_body) do
+          {
+            jsonrpc: "2.0",
+            method: "initialize",
+            id: 1
+          }.to_json
+        end
+
+        it "returns server information" do
+          post api_mcp_path, params: request_body, headers: headers
+
+          expect(response).to have_http_status(:success)
+
+          json_response = JSON.parse(response.body)
+          expect(json_response["jsonrpc"]).to eq("2.0")
+          expect(json_response["id"]).to eq(1)
+          expect(json_response["result"]["protocolVersion"]).to eq("2024-11-05")
+          expect(json_response["result"]["serverInfo"]["name"]).to eq("spotlight-rails-articles")
+        end
+      end
+
+      context "when handling tools list request" do
+        let(:request_body) do
+          {
+            jsonrpc: "2.0",
+            method: "tools/list",
+            id: 2
+          }.to_json
+        end
+
+        it "returns available tools" do
+          post api_mcp_path, params: request_body, headers: headers
+
+          expect(response).to have_http_status(:success)
+
+          json_response = JSON.parse(response.body)
+          expect(json_response["jsonrpc"]).to eq("2.0")
+          expect(json_response["id"]).to eq(2)
+
+          tools = json_response["result"]["tools"]
+          expect(tools).to be_an(Array)
+          expect(tools.map { |t| t["name"] }).to include("create_article_tool", "update_article_tool", "find_article_tool")
+        end
+      end
+
+      context "when calling create_article_tool" do
+        let(:request_body) do
+          {
+            jsonrpc: "2.0",
+            method: "tools/call",
+            params: {
+              name: "create_article_tool",
+              arguments: {
+                content: <<~MARKDOWN
+                  ---
+                  title: "Test Article"
+                  slug: test-article
+                  category: article
+                  description: "A test article"
+                  published_date: 2025-01-12
+                  tags:
+                    - Rails
+                    - Testing
+                  ---
+
+                  ## Test Content
+
+                  This is a test article.
+                MARKDOWN
+              }
+            },
+            id: 3
+          }.to_json
+        end
+
+        it "creates a new article" do
+          expect {
+            post api_mcp_path, params: request_body, headers: headers
+          }.to change(Article, :count).by(1)
+
+          expect(response).to have_http_status(:success)
+
+          json_response = JSON.parse(response.body)
+          expect(json_response["jsonrpc"]).to eq("2.0")
+          expect(json_response["id"]).to eq(3)
+          expect(json_response["result"]["content"][0]["text"]).to include("Article created successfully")
+
+          article = Article.last
+          expect(article.title).to eq("Test Article")
+          expect(article.slug).to eq("test-article")
+          expect(article.tags.map(&:name)).to match_array([ "Rails", "Testing" ])
+        end
+      end
+
+      context "when handling invalid JSON-RPC request" do
+        let(:request_body) { "invalid json" }
+
+        it "returns JSON-RPC parse error" do
+          post api_mcp_path, params: request_body, headers: headers
+
+          expect(response).to have_http_status(:success)
+
+          json_response = JSON.parse(response.body)
+          expect(json_response["error"]["code"]).to eq(-32700)
+          expect(json_response["error"]["message"]).to eq("Parse error")
+        end
+      end
+
+      context "when server raises an error" do
+        let(:request_body) do
+          {
+            jsonrpc: "2.0",
+            method: "unknown_method",
+            id: 4
+          }.to_json
+        end
+
+        before do
+          allow_any_instance_of(MCP::Server).to receive(:handle_json).and_raise(StandardError.new("Test error"))
+        end
+
+        it "returns internal server error" do
+          post api_mcp_path, params: request_body, headers: headers
+
+          expect(response).to have_http_status(:internal_server_error)
+
+          json_response = JSON.parse(response.body)
+          expect(json_response["error"]["code"]).to eq(-32603)
+          expect(json_response["error"]["message"]).to eq("Internal error")
+          expect(json_response["error"]["data"]["details"]).to eq("Test error")
+        end
+      end
+    end
+
+    context "with invalid authentication" do
+      context "when token is missing" do
+        let(:headers) { { "Content-Type" => "application/json" } }
+        let(:request_body) do
+          {
+            jsonrpc: "2.0",
+            method: "initialize",
+            id: 1
+          }.to_json
+        end
+
+        it "returns unauthorized error" do
+          post api_mcp_path, params: request_body, headers: headers
+
+          expect(response).to have_http_status(:unauthorized)
+
+          json_response = JSON.parse(response.body)
+          expect(json_response["error"]["code"]).to eq(-32603)
+          expect(json_response["error"]["message"]).to eq("Unauthorized")
+          expect(json_response["error"]["data"]["details"]).to eq("Invalid or missing authentication token")
+        end
+      end
+
+      context "when token is invalid" do
+        let(:headers) { { "Authorization" => "Bearer invalid-token", "Content-Type" => "application/json" } }
+        let(:request_body) do
+          {
+            jsonrpc: "2.0",
+            method: "initialize",
+            id: 1
+          }.to_json
+        end
+
+        it "returns unauthorized error" do
+          post api_mcp_path, params: request_body, headers: headers
+
+          expect(response).to have_http_status(:unauthorized)
+
+          json_response = JSON.parse(response.body)
+          expect(json_response["error"]["code"]).to eq(-32603)
+          expect(json_response["error"]["message"]).to eq("Unauthorized")
+        end
+      end
+    end
+
+    context "with non-Bearer authentication scheme" do
+      let(:headers) { { "Authorization" => "Basic #{valid_token}", "Content-Type" => "application/json" } }
+      let(:request_body) do
+        {
+          jsonrpc: "2.0",
+          method: "initialize",
+          id: 1
+        }.to_json
+      end
+
+      it "returns unauthorized error" do
+        post api_mcp_path, params: request_body, headers: headers
+
+        expect(response).to have_http_status(:unauthorized)
+      end
+    end
+  end
+end