Class: MCPClient::Client

Inherits:
Object
  • Object
show all
Defined in:
lib/mcp_client/client.rb

Overview

MCP Client for integrating with the Model Context Protocol This is the main entry point for using MCP tools

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(mcp_server_configs: [], logger: nil, elicitation_handler: nil, roots: nil, sampling_handler: nil) ⇒ Client

Initialize a new MCPClient::Client



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# File 'lib/mcp_client/client.rb', line 29

def initialize(mcp_server_configs: [], logger: nil, elicitation_handler: nil, roots: nil, sampling_handler: nil)
  @logger = logger || Logger.new($stdout, level: Logger::WARN)
  @logger.progname = self.class.name
  @logger.formatter = proc { |severity, _datetime, progname, msg| "#{severity} [#{progname}] #{msg}\n" }
  @servers = mcp_server_configs.map do |config|
    @logger.debug("Creating server with config: #{config.inspect}")
    MCPClient::ServerFactory.create(config, logger: @logger)
  end
  @tool_cache = {}
  @prompt_cache = {}
  @resource_cache = {}
  # JSON-RPC notification listeners
  @notification_listeners = []
  # Elicitation handler (MCP 2025-06-18)
  @elicitation_handler = elicitation_handler
  # Sampling handler (MCP 2025-06-18)
  @sampling_handler = sampling_handler
  # Roots (MCP 2025-06-18)
  @roots = normalize_roots(roots)
  # Register default and user-defined notification handlers on each server
  @servers.each do |server|
    server.on_notification do |method, params|
      # Default notification processing (e.g., cache invalidation, logging)
      process_notification(server, method, params)
      # Invoke user-defined listeners
      @notification_listeners.each { |cb| cb.call(server, method, params) }
    end
    # Register elicitation handler on each server
    if server.respond_to?(:on_elicitation_request)
      server.on_elicitation_request(&method(:handle_elicitation_request))
    end
    # Register roots list handler on each server (MCP 2025-06-18)
    server.on_roots_list_request(&method(:handle_roots_list_request)) if server.respond_to?(:on_roots_list_request)
    # Register sampling handler on each server (MCP 2025-06-18)
    server.on_sampling_request(&method(:handle_sampling_request)) if server.respond_to?(:on_sampling_request)
  end
end

Instance Attribute Details

#logger ⇒ Logger (readonly) 



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# File 'lib/mcp_client/client.rb', line 21

attr_reader :servers, :tool_cache, :prompt_cache, :resource_cache, :logger, :roots

#prompt_cache ⇒ Hash<String, MCPClient::Prompt> (readonly) 



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# File 'lib/mcp_client/client.rb', line 21

attr_reader :servers, :tool_cache, :prompt_cache, :resource_cache, :logger, :roots

#resource_cache ⇒ Hash<String, MCPClient::Resource> (readonly) 



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# File 'lib/mcp_client/client.rb', line 21

attr_reader :servers, :tool_cache, :prompt_cache, :resource_cache, :logger, :roots

#roots ⇒ Object

Returns the value of attribute roots.



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# File 'lib/mcp_client/client.rb', line 21

attr_reader :servers, :tool_cache, :prompt_cache, :resource_cache, :logger, :roots

#servers ⇒ Array<MCPClient::ServerBase> (readonly) 



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# File 'lib/mcp_client/client.rb', line 21

def servers
  @servers
end

#tool_cache ⇒ Hash<String, MCPClient::Tool> (readonly) 



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# File 'lib/mcp_client/client.rb', line 21

attr_reader :servers, :tool_cache, :prompt_cache, :resource_cache, :logger, :roots

Instance Method Details

#call_tool(tool_name, parameters, server: nil) ⇒ Object

Calls a specific tool by name with the given parameters

Raises:



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# File 'lib/mcp_client/client.rb', line 253

def call_tool(tool_name, parameters, server: nil)
  tools = list_tools

  if server
    # Use the specified server
    srv = select_server(server)
    # Find the tool on this specific server
    tool = tools.find { |t| t.name == tool_name && t.server == srv }
    unless tool
      raise MCPClient::Errors::ToolNotFound,
            "Tool '#{tool_name}' not found on server '#{srv.name || srv.class.name}'"
    end
  else
    # Find the tool across all servers
    matching_tools = tools.select { |t| t.name == tool_name }

    if matching_tools.empty?
      raise MCPClient::Errors::ToolNotFound, "Tool '#{tool_name}' not found"
    elsif matching_tools.size > 1
      # If multiple matches, disambiguate with server names
      server_names = matching_tools.map { |t| t.server&.name || 'unnamed' }
      raise MCPClient::Errors::AmbiguousToolName,
            "Multiple tools named '#{tool_name}' found across servers (#{server_names.join(', ')}). " \
            "Please specify a server using the 'server' parameter."
    end

    tool = matching_tools.first
  end

  # Validate parameters against tool schema
  validate_params!(tool, parameters)

  # Use the tool's associated server
  server = tool.server
  raise MCPClient::Errors::ServerNotFound, "No server found for tool '#{tool_name}'" unless server

  begin
    server.call_tool(tool_name, parameters)
  rescue MCPClient::Errors::ConnectionError => e
    # Add server identity information to the error for better context
    server_id = server.name ? "#{server.class}[#{server.name}]" : server.class.name
    raise MCPClient::Errors::ToolCallError, "Error calling tool '#{tool_name}': #{e.message} (Server: #{server_id})"
  end
end

#call_tool_streaming(tool_name, parameters, server: nil) ⇒ Enumerator

Stream call of a specific tool by name with the given parameters. Returns an Enumerator yielding streaming updates if supported.

Raises:



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# File 'lib/mcp_client/client.rb', line 398

def call_tool_streaming(tool_name, parameters, server: nil)
  tools = list_tools

  if server
    # Use the specified server
    srv = select_server(server)
    # Find the tool on this specific server
    tool = tools.find { |t| t.name == tool_name && t.server == srv }
    unless tool
      raise MCPClient::Errors::ToolNotFound,
            "Tool '#{tool_name}' not found on server '#{srv.name || srv.class.name}'"
    end
  else
    # Find the tool across all servers
    matching_tools = tools.select { |t| t.name == tool_name }

    if matching_tools.empty?
      raise MCPClient::Errors::ToolNotFound, "Tool '#{tool_name}' not found"
    elsif matching_tools.size > 1
      # If multiple matches, disambiguate with server names
      server_names = matching_tools.map { |t| t.server&.name || 'unnamed' }
      raise MCPClient::Errors::AmbiguousToolName,
            "Multiple tools named '#{tool_name}' found across servers (#{server_names.join(', ')}). " \
            "Please specify a server using the 'server' parameter."
    end

    tool = matching_tools.first
  end

  # Validate parameters against tool schema
  validate_params!(tool, parameters)

  # Use the tool's associated server
  server = tool.server
  raise MCPClient::Errors::ServerNotFound, "No server found for tool '#{tool_name}'" unless server

  begin
    # Use the streaming API if it's available
    server.call_tool_streaming(tool_name, parameters)
  rescue MCPClient::Errors::ConnectionError => e
    # Add server identity information to the error for better context
    server_id = server.name ? "#{server.class}[#{server.name}]" : server.class.name
    msg = "Error calling streaming tool '#{tool_name}': #{e.message} (Server: #{server_id})"
    raise MCPClient::Errors::ToolCallError, msg
  end
end

#call_tools(calls) ⇒ Array<Object>

Call multiple tools in batch



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# File 'lib/mcp_client/client.rb', line 383

def call_tools(calls)
  calls.map do |call|
    name = call[:name] || call['name']
    params = call[:parameters] || call['parameters'] || {}
    server = call[:server] || call['server']
    call_tool(name, params, server: server)
  end
end

#cleanup ⇒ Object

Clean up all server connections



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# File 'lib/mcp_client/client.rb', line 326

def cleanup
  servers.each(&:cleanup)
end

#clear_cache ⇒ void

This method returns an undefined value.

Clear the cached tools so that next list_tools will fetch fresh data



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# File 'lib/mcp_client/client.rb', line 332

def clear_cache
  @tool_cache.clear
  @prompt_cache.clear
  @resource_cache.clear
end

#complete(ref:, argument:, server: nil) ⇒ Hash

Request completion suggestions from a server (MCP 2025-06-18)

Raises:



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# File 'lib/mcp_client/client.rb', line 493

def complete(ref:, argument:, server: nil)
  srv = select_server(server)
  srv.complete(ref: ref, argument: argument)
end

#find_server(name) ⇒ MCPClient::ServerBase?

Find a server by name



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# File 'lib/mcp_client/client.rb', line 358

def find_server(name)
  @servers.find { |s| s.name == name }
end

#find_tool(pattern) ⇒ MCPClient::Tool?

Find the first tool whose name matches the given pattern



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# File 'lib/mcp_client/client.rb', line 373

def find_tool(pattern)
  find_tools(pattern).first
end

#find_tools(pattern) ⇒ Array<MCPClient::Tool>

Find all tools whose name matches the given pattern (String or Regexp)



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# File 'lib/mcp_client/client.rb', line 365

def find_tools(pattern)
  rx = pattern.is_a?(Regexp) ? pattern : /#{Regexp.escape(pattern)}/
  list_tools.select { |t| t.name.match(rx) }
end

#get_prompt(prompt_name, parameters, server: nil) ⇒ Object

Gets a specific prompt by name with the given parameters

Raises:



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# File 'lib/mcp_client/client.rb', line 103

def get_prompt(prompt_name, parameters, server: nil)
  prompts = list_prompts

  if server
    # Use the specified server
    srv = select_server(server)
    # Find the prompt on this specific server
    prompt = prompts.find { |t| t.name == prompt_name && t.server == srv }
    unless prompt
      raise MCPClient::Errors::PromptNotFound,
            "Prompt '#{prompt_name}' not found on server '#{srv.name || srv.class.name}'"
    end
  else
    # Find the prompt across all servers
    matching_prompts = prompts.select { |t| t.name == prompt_name }

    if matching_prompts.empty?
      raise MCPClient::Errors::PromptNotFound, "Prompt '#{prompt_name}' not found"
    elsif matching_prompts.size > 1
      # If multiple matches, disambiguate with server names
      server_names = matching_prompts.map { |t| t.server&.name || 'unnamed' }
      raise MCPClient::Errors::AmbiguousPromptName,
            "Multiple prompts named '#{prompt_name}' found across servers (#{server_names.join(', ')}). " \
            "Please specify a server using the 'server' parameter."
    end

    prompt = matching_prompts.first
  end

  # Use the prompt's associated server
  server = prompt.server
  raise MCPClient::Errors::ServerNotFound, "No server found for prompt '#{prompt_name}'" unless server

  begin
    server.get_prompt(prompt_name, parameters)
  rescue MCPClient::Errors::ConnectionError => e
    # Add server identity information to the error for better context
    server_id = server.name ? "#{server.class}[#{server.name}]" : server.class.name
    raise MCPClient::Errors::PromptGetError,
          "Error getting prompt '#{prompt_name}': #{e.message} (Server: #{server_id})"
  end
end

#list_prompts(cache: true) ⇒ Array<MCPClient::Prompt>

Lists all available prompts from all connected MCP servers

Raises:



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# File 'lib/mcp_client/client.rb', line 72

def list_prompts(cache: true)
  return @prompt_cache.values if cache && !@prompt_cache.empty?

  prompts = []
  connection_errors = []

  servers.each do |server|
    server.list_prompts.each do |prompt|
      cache_key = cache_key_for(server, prompt.name)
      @prompt_cache[cache_key] = prompt
      prompts << prompt
    end
  rescue MCPClient::Errors::ConnectionError => e
    # Fast-fail on authorization errors for better user experience
    # If this is the first server or we haven't collected any prompts yet,
    # raise the auth error directly to avoid cascading error messages
    raise e if e.message.include?('Authorization failed') && prompts.empty?

    # Store the error and try other servers
    connection_errors << e
    @logger.error("Server error: #{e.message}")
  end

  prompts
end

#list_resources(cache: true, cursor: nil) ⇒ Hash

Lists all available resources from all connected MCP servers

Raises:



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# File 'lib/mcp_client/client.rb', line 152

def list_resources(cache: true, cursor: nil)
  # If cursor is provided, we can only query one server (the one that provided the cursor)
  # This is a limitation of aggregating multiple servers
  if cursor
    # For now, just use the first server when cursor is provided
    # In a real implementation, you'd need to track which server the cursor came from
    return servers.first.list_resources(cursor: cursor) if servers.any?

    return { 'resources' => [], 'nextCursor' => nil }
  end

  # Use cache if available and no cursor
  return { 'resources' => @resource_cache.values, 'nextCursor' => nil } if cache && !@resource_cache.empty?

  resources = []
  connection_errors = []

  servers.each do |server|
    result = server.list_resources
    resource_list = result['resources'] || []

    resource_list.each do |resource|
      cache_key = cache_key_for(server, resource.uri)
      @resource_cache[cache_key] = resource
      resources << resource
    end
  rescue MCPClient::Errors::ConnectionError => e
    # Fast-fail on authorization errors for better user experience
    # If this is the first server or we haven't collected any resources yet,
    # raise the auth error directly to avoid cascading error messages
    raise e if e.message.include?('Authorization failed') && resources.empty?

    # Store the error and try other servers
    connection_errors << e
    @logger.error("Server error: #{e.message}")
  end

  # Return hash format consistent with server methods
  { 'resources' => resources, 'nextCursor' => nil }
end

#list_tools(cache: true) ⇒ Array<MCPClient::Tool>

Lists all available tools from all connected MCP servers

Raises:



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# File 'lib/mcp_client/client.rb', line 215

def list_tools(cache: true)
  return @tool_cache.values if cache && !@tool_cache.empty?

  tools = []
  connection_errors = []

  servers.each do |server|
    server.list_tools.each do |tool|
      cache_key = cache_key_for(server, tool.name)
      @tool_cache[cache_key] = tool
      tools << tool
    end
  rescue MCPClient::Errors::ConnectionError => e
    # Fast-fail on authorization errors for better user experience
    # If this is the first server or we haven't collected any tools yet,
    # raise the auth error directly to avoid cascading error messages
    raise e if e.message.include?('Authorization failed') && tools.empty?

    # Store the error and try other servers
    connection_errors << e
    @logger.error("Server error: #{e.message}")
  end

  # If we didn't get any tools from any server but have servers configured, report failure
  if tools.empty? && !servers.empty?
    raise connection_errors.first if connection_errors.any?

    @logger.warn('No tools found from any server.')
  end

  tools
end

#log_level=(level) ⇒ Array<Hash>

Set the logging level on all connected servers (MCP 2025-06-18) To set on a specific server, use: client.find_server(‘name’).log_level = ‘debug’

Raises:



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# File 'lib/mcp_client/client.rb', line 504

def log_level=(level)
  @servers.map { |srv| srv.log_level = level }
end

#on_notification {|server, method, params| ... } ⇒ void

This method returns an undefined value.

Register a callback for JSON-RPC notifications from servers

Yields:

  • (server, method, params) 


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# File 'lib/mcp_client/client.rb', line 341

def on_notification(&block)
  @notification_listeners << block
end

#ping(server_index: nil) ⇒ Object

Ping the MCP server to check connectivity (zero-parameter heartbeat call)

Raises:



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# File 'lib/mcp_client/client.rb', line 449

def ping(server_index: nil)
  if server_index.nil?
    # Ping first available server
    raise MCPClient::Errors::ServerNotFound, 'No server available for ping' if @servers.empty?

    @servers.first.ping
  else
    # Ping specified server
    if server_index >= @servers.length
      raise MCPClient::Errors::ServerNotFound,
            "Server at index #{server_index} not found"
    end

    @servers[server_index].ping
  end
end

#read_resource(uri, server: nil) ⇒ Object

Reads a specific resource by URI



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# File 'lib/mcp_client/client.rb', line 197

def read_resource(uri, server: nil)
  result = list_resources
  resources = result['resources'] || []

  resource = if server
               find_resource_on_server(uri, resources, server)
             else
               find_resource_across_servers(uri, resources)
             end

  execute_resource_read(resource, uri)
end

#send_notification(method, params: {}, server: nil) ⇒ void

This method returns an undefined value.

Send a raw JSON-RPC notification to a server (no response expected)



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# File 'lib/mcp_client/client.rb', line 481

def send_notification(method, params: {}, server: nil)
  srv = select_server(server)
  srv.rpc_notify(method, params)
end

#send_rpc(method, params: {}, server: nil) ⇒ Object

Send a raw JSON-RPC request to a server



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# File 'lib/mcp_client/client.rb', line 471

def send_rpc(method, params: {}, server: nil)
  srv = select_server(server)
  srv.rpc_request(method, params)
end

#to_anthropic_tools(tool_names: nil) ⇒ Array<Hash>

Convert MCP tools to Anthropic Claude tool specifications



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# File 'lib/mcp_client/client.rb', line 310

def to_anthropic_tools(tool_names: nil)
  tools = list_tools
  tools = tools.select { |t| tool_names.include?(t.name) } if tool_names
  tools.map(&:to_anthropic_tool)
end

#to_google_tools(tool_names: nil) ⇒ Array<Hash>

Convert MCP tools to Google Vertex AI tool specifications



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# File 'lib/mcp_client/client.rb', line 319

def to_google_tools(tool_names: nil)
  tools = list_tools
  tools = tools.select { |t| tool_names.include?(t.name) } if tool_names
  tools.map(&:to_google_tool)
end

#to_openai_tools(tool_names: nil) ⇒ Array<Hash>

Convert MCP tools to OpenAI function specifications



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# File 'lib/mcp_client/client.rb', line 301

def to_openai_tools(tool_names: nil)
  tools = list_tools
  tools = tools.select { |t| tool_names.include?(t.name) } if tool_names
  tools.map(&:to_openai_tool)
end