refactor: Implement prompt functionality feedback

Key changes:
- Added robust prompt registration and handling in Server class
- Implemented base64 validation for image content to ensure MCP compliance
- Simplified messages API to use only keyword arguments for better usability
- Refactored code to follow DRY principles and improve maintainability
- Updated tool_name method to follow the same pattern as prompt_name
- Fixed unused parameters and linter warnings throughout the codebase
- Added comprehensive test coverage for all new functionality
- Added example prompts to demo files for easy adoption
- Reverted version to 1.0.0 as requested by maintainer

This implementation enables developers to create and register prompts that can
generate messages with text, image, and resource content, following the MCP
specification. The code is thoroughly tested and includes examples to
demonstrate proper usage.

All tasks from PR yjacquin#21 feedback have been addressed

Author: cs3b

CHANGELOG.md

@@ -5,7 +5,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [1.2.0] - 2025-04-14
+## [Unreleased]
 
 ### Added
 - Prompts Feature 
@@ -40,7 +40,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Namespace consistency correction (FastMCP -> FastMcp) throughout the codebase
 
 ### Improved
-- ⚠️ [Breaking] Resource content declaration changes
+- [Breaking] Resource content declaration changes
   - Now resources implement `content` over `default_content`
   - `content` is dynamically called when calling a resource, this implies we can declare dynamic resource contents like:
   ```ruby

Gemfile.lock

@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    fast-mcp (1.1.0)
+    fast-mcp (1.0.0)
       base64
       dry-schema (~> 1.14)
       json (~> 2.0)

README.md

@@ -219,6 +219,29 @@ end
 # Register the resource with the server
 server.register_resource(StatisticsResource)
 
+# Define a prompt by inheriting from FastMcp::Prompt
+class GreetingPrompt < FastMcp::Prompt
+  prompt_name 'greeting'
+  description 'A friendly greeting prompt'
+  
+  arguments do
+    required(:name).filled(:string).description("User's name")
+    optional(:time_of_day).filled(:string).description("Morning, afternoon, or evening")
+  end
+  
+  def call(name:, time_of_day: nil)
+    greeting = time_of_day ? "Good #{time_of_day}" : "Hello"
+    
+    messages(
+      assistant: "#{greeting}, #{name}! How can I help you today?",
+      user: "I'd like some assistance with Ruby programming."
+    )
+  end
+end
+
+# Register the prompt with the server
+server.register_prompt(GreetingPrompt)
+
 # Start the server
 server.start
 ```
@@ -388,7 +411,4 @@ This project is available as open source under the terms of the [MIT License](ht
 
 - The [Model Context Protocol](https://github.com/modelcontextprotocol) team for creating the specification
 - The [Dry-Schema](https://github.com/dry-rb/dry-schema) team for the argument validation.
-- All contributors to this project
-
-## How to add a MCP server to Claude, Cursor, or other MCP clients?
-Please refer to [configuring_mcp_clients](docs/configuring_mcp_clients.md)
+- All contributors to this project

examples/authenticated_rack_middleware.rb

@@ -59,6 +59,35 @@ def content
   end
 end
 
+# Example prompt that uses inline text instead of ERB templates
+class InlinePrompt < FastMcp::Prompt
+  prompt_name 'inline_example'
+  description 'An example prompt that uses inline text instead of ERB templates'
+  
+  arguments do
+    required(:query).description('The user query to respond to')
+    optional(:context).description('Additional context for the response')
+  end
+
+  def call(query:, context: nil)
+    # Create assistant message
+    assistant_message = "I'll help you answer your question about: #{query}"
+    
+    # Create user message
+    user_message = if context
+                     "My question is: #{query}\nHere's some additional context: #{context}"
+                   else
+                     "My question is: #{query}"
+                   end
+
+    # Using the messages method with a hash
+    messages(
+      assistant: assistant_message,
+      user: user_message
+    )
+  end
+end
+
 # Create a simple Rack application
 app = lambda do |_env|
   [200, { 'Content-Type' => 'text/html' },
@@ -73,6 +102,9 @@ def content
 
   # Register a sample resource
   server.register_resource(HelloWorldResource)
+
+  # Register the inline prompt
+  server.register_prompt(InlinePrompt)
 end
 
 # Run the Rack application with Puma

examples/prompts/multi_message_prompt.rb

@@ -59,6 +59,35 @@ def content
   end
 end
 
+# Example prompt that uses inline text instead of ERB templates
+class InlinePrompt < FastMcp::Prompt
+  prompt_name 'inline_example'
+  description 'An example prompt that uses inline text instead of ERB templates'
+  
+  arguments do
+    required(:query).description('The user query to respond to')
+    optional(:context).description('Additional context for the response')
+  end
+
+  def call(query:, context: nil)
+    # Create assistant message
+    assistant_message = "I'll help you answer your question about: #{query}"
+    
+    # Create user message
+    user_message = if context
+                     "My question is: #{query}\nHere's some additional context: #{context}"
+                   else
+                     "My question is: #{query}"
+                   end
+
+    # Using the messages method with a hash
+    messages(
+      assistant: assistant_message,
+      user: user_message
+    )
+  end
+end
+
 # Create a simple Rack application
 app = lambda do |_env|
   [200, { 'Content-Type' => 'text/html' },
@@ -76,6 +105,9 @@ def content
 
   # Register a sample resource
   server.register_resource(HelloWorldResource)
+
+  # Register a sample prompt
+  server.register_prompt(InlinePrompt)
 end
 
 # Run the Rack application with Puma

examples/rack_middleware.rb

@@ -77,7 +77,37 @@ def content
   end
 end
 
+# Example prompt that uses inline text instead of ERB templates
+class InlinePrompt < FastMcp::Prompt
+  prompt_name 'inline_example'
+  description 'An example prompt that uses inline text instead of ERB templates'
+  
+  arguments do
+    required(:query).description('The user query to respond to')
+    optional(:context).description('Additional context for the response')
+  end
+
+  def call(query:, context: nil)
+    # Create assistant message
+    assistant_message = "I'll help you answer your question about: #{query}"
+    
+    # Create user message
+    user_message = if context
+                     "My question is: #{query}\nHere's some additional context: #{context}"
+                   else
+                     "My question is: #{query}"
+                   end
+
+    # Using the messages method with a hash
+    messages(
+      assistant: assistant_message,
+      user: user_message
+    )
+  end
+end
+
 server.register_resources(CounterResource, UsersResource, WeatherResource)
+server.register_prompts(InlinePrompt)
 
 # Class-based tool for incrementing the counter
 class IncrementCounterTool < FastMcp::Tool

examples/server_with_stdio_transport.rb

@@ -2,6 +2,7 @@
 
 require 'dry-schema'
 require 'erb'
+require 'base64'
 
 module FastMcp
   # Main Prompt class that represents an MCP Prompt
@@ -77,72 +78,30 @@ def message(role:, content:)
       }
     end
 
-    # Create multiple messages from a hash of role => content pairs or an array of role-keyed hashes
-    # @param args [Hash, Array<Hash>] Either a hash of role => content pairs or an array of single-key hashes with role as key
+    # Create multiple messages from a hash of role => content pairs
+    # @param messages_hash [Hash] A hash of role => content pairs
     # @return [Array<Hash>] An array of messages
-    def messages(*args)
-      result = []
+    def messages(messages_hash)
+      raise ArgumentError, 'At least one message must be provided' if messages_hash.empty?
 
-      # Handle both hash and array arguments for backward compatibility
-      if args.length == 1 && args.first.is_a?(Hash)
-        # Original API: hash of role => content pairs
-        messages_hash = args.first
-        raise ArgumentError, 'At least one message must be provided' if messages_hash.empty?
-        
-        messages_hash.each do |role_key, content|
-          # Extract the base role (without any suffix like _2)
-          base_role = role_key.to_s.gsub(/_\d+$/, '')
-          
-          # Validate the role
-          validate_role(base_role)
-          
-          # Add the message to the result
-          if content.is_a?(Hash)
-            result << message(role: base_role, content: content)
-          else
-            result << message(role: base_role, content: text_content(content))
-          end
-        end
-      else
-        # New API: array of single-key hashes with role as key
-        raise ArgumentError, 'At least one message must be provided' if args.empty?
-        
-        args.each do |msg_hash|
-          raise ArgumentError, 'Each message must be a hash' unless msg_hash.is_a?(Hash)
-          
-          # Each hash should have a single key (the role)
-          msg_hash.each do |role_key, content|
-            # Extract the base role (without any suffix like _2)
-            base_role = role_key.to_s.gsub(/_\d+$/, '')
-            
-            # Validate the role
-            validate_role(base_role)
-            
-            # Add the message to the result
-            if content.is_a?(Hash)
-              result << message(role: base_role, content: content)
-            else
-              result << message(role: base_role, content: text_content(content))
-            end
-          end
-        end
+      messages_hash.map do |role_key, content|
+        role = role_key.to_s.gsub(/_\d+$/, '').to_sym
+        { role: ROLES.fetch(role), content: content_from(content) }
       end
-
-      result
     end
 
     # Helper method to extract content from a hash
-    def content_from_hash(hash)
-      if hash.key?(:text)
-        text_content(hash[:text])
-      elsif hash.key?(:data) && hash.key?(:mimeType)
-        image_content(hash[:data], hash[:mimeType])
-      elsif hash.key?(:resource)
-        # It's already a resource content
+    def content_from(content)
+      if content.is_a?(String)
+        text_content(content)
+      elsif content.key?(:text)
+        text_content(content[:text])
+      elsif content.key?(:data) && content.key?(:mimeType)
+        image_content(content[:data], content[:mimeType])
+      elsif content.key?(:resource)
         hash
       else
-        # Default to text content with empty string
-        text_content('')
+        text_content('unsupported content')
       end
     end
 
@@ -200,6 +159,19 @@ def validate_content(content)
       when CONTENT_TYPE_IMAGE
         raise ArgumentError, "Missing :data in image content" unless content[:data]
         raise ArgumentError, "Missing :mimeType in image content" unless content[:mimeType]
+        
+        # Validate that data is a string
+        unless content[:data].is_a?(String)
+          raise ArgumentError, "Image :data must be a string containing base64-encoded data"
+        end
+        
+        # Validate that data is valid base64
+        begin
+          # Try to decode the base64 data
+          Base64.strict_decode64(content[:data])
+        rescue ArgumentError
+          raise ArgumentError, "Image :data must be valid base64-encoded data"
+        end
       when CONTENT_TYPE_RESOURCE
         validate_resource_content(content[:resource])
       else