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topherbullocktopherbullock
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add client
add a client with http transport
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‎examples/http_client_example.rb‎

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#!/usr/bin/env ruby
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# frozen_string_literal: true
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require_relative "../lib/mcp"
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# Example of using the MCP HTTP client
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def main
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# Create an HTTP transport pointing to your MCP server
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transport = MCP::Client::Transports::HTTP.new(
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url: "http://localhost:3000/mcp",
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timeout: 30,
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headers: {
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"Authorization" => "Bearer your-token-here", # Optional authentication
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},
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)
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# Create the client with the transport
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client = MCP::Client.new(transport: transport)
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begin
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puts "Pinging..."
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client.ping(request_id: "ping-001")
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# Initialize the session
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puts "Initializing session..."
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result = client.initialize_session(
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protocol_version: "2025-03-26",
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capabilities: {},
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client_info: {
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name: "example_client",
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version: "1.0.0",
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},
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request_id: "init-001", # Custom request ID
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)
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puts "Connected to server: #{client.server_info[:name]} v#{client.server_info[:version]}"
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puts "Protocol version: #{result[:protocolVersion]}"
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puts "Server capabilities: #{client.capabilities.keys.join(", ")}"
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# List available tools
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if client.capabilities[:tools]
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puts "Listing tools..."
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tools_result = client.list_tools(request_id: "tools-list-001")
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tools = tools_result[:tools] || []
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if tools.any?
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tools.each do |tool|
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puts "- #{tool[:name]}: #{tool[:description]}"
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end
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else
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puts "No tools available"
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end
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puts
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# Call a tool if available
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if tools.any?
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tool_name = tools.first[:name]
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puts "Calling tool: #{tool_name}"
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begin
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result = client.call_tool(
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name: tool_name,
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arguments: {},
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request_id: "tool-call-001", # Custom request ID
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)
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puts "Tool result: #{result}"
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rescue MCP::Client::ClientError => e
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puts "Tool call failed: #{e.message}"
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end
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puts
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end
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end
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# List available prompts (using auto-incrementing ID)
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if client.capabilities[:prompts]
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puts "Listing prompts..."
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prompts_result = client.list_prompts # No custom ID - will auto-increment
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prompts = prompts_result[:prompts] || []
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if prompts.any?
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prompts.each do |prompt|
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puts "- #{prompt[:name]}: #{prompt[:description]}"
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end
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else
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puts "No prompts available"
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end
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puts
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# Get a prompt if available
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if prompts.any?
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prompt_name = prompts.first[:name]
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puts "Getting prompt: #{prompt_name}"
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begin
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result = client.get_prompt(
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name: prompt_name,
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arguments: {},
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request_id: "prompt-get-001", # Custom request ID
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)
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puts "Prompt result: #{result[:description]}"
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puts "Messages: #{result[:messages].length} message(s)"
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rescue MCP::Client::ClientError => e
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puts "Prompt get failed: #{e.message}"
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end
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puts
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end
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end
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# List available resources
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if client.capabilities[:resources]
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puts "Listing resources..."
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resources_result = client.list_resources # Auto-incrementing ID
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resources = resources_result[:resources] || []
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if resources.any?
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resources.each do |resource|
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puts "- #{resource[:uri]}: #{resource[:name]} (#{resource[:mimeType]})"
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end
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else
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puts "No resources available"
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end
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puts
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# Read a resource if available
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if resources.any?
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resource_uri = resources.first[:uri]
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puts "Reading resource: #{resource_uri}"
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begin
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result = client.read_resource(
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uri: resource_uri,
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request_id: "resource-read-001", # Custom request ID
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)
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contents = result[:contents] || []
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contents.each do |content|
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puts "Content type: #{content[:mimeType]}"
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if content[:text]
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puts "Text content: #{content[:text][0..100]}#{"..." if content[:text].length > 100}"
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elsif content[:blob]
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puts "Binary content: #{content[:blob].length} bytes"
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end
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end
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rescue MCP::Client::ClientError => e
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puts "Resource read failed: #{e.message}"
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end
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puts
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end
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end
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rescue MCP::Client::ClientError => e
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puts "Client error: #{e.message}"
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exit(1)
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rescue MCP::Client::Transports::HTTP::HTTPError => e
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puts "HTTP error: #{e.message}"
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puts "Status code: #{e.status_code}" if e.status_code
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exit(1)
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rescue => e
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puts "Unexpected error: #{e.message}"
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puts e.backtrace.join("\n")
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exit(1)
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end
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end
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if __FILE__ == $0
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main
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end

‎lib/mcp.rb‎

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# frozen_string_literal: true
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require_relative "mcp/server"
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require_relative "mcp/client"
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require_relative "mcp/client/transports/http"
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require_relative "mcp/string_utils"
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require_relative "mcp/tool"
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require_relative "mcp/tool/input_schema"

‎lib/mcp/client.rb‎

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# frozen_string_literal: true
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require "json"
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require_relative "methods"
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module MCP
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class Client
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class ClientError < StandardError
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attr_reader :error_type, :original_error
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def initialize(message, error_type: :client_error, original_error: nil)
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super(message)
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@error_type = error_type
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@original_error = original_error
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end
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end
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attr_reader :transport, :server_info, :capabilities
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def initialize(transport:)
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@transport = transport
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@request_id = 0
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@server_info = nil
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@capabilities = nil
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end
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def initialize_session(protocol_version: "2025-03-26", capabilities: {}, client_info: {}, request_id: nil)
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params = {
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protocolVersion: protocol_version,
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capabilities: capabilities,
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clientInfo: client_info,
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}
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request = build_request(Methods::INITIALIZE, params, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new(
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"Failed to initialize: #{response[:error][:message]}",
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error_type: :initialization_error,
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)
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end
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result = response[:result]
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@server_info = result[:serverInfo]
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@capabilities = result[:capabilities]
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result
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end
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def ping(request_id: nil)
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request = build_request(Methods::PING, nil, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Ping failed: #{response[:error][:message]}")
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end
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response[:result]
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end
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def list_tools(cursor: nil, request_id: nil)
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params = cursor ? { cursor: cursor } : nil
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request = build_request(Methods::TOOLS_LIST, params, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to list tools: #{response[:error][:message]}")
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end
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response[:result]
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end
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def call_tool(name:, arguments: {}, request_id: nil)
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params = { name: name }
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params[:arguments] = arguments unless arguments.empty?
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request = build_request(Methods::TOOLS_CALL, params, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to call tool '#{name}': #{response[:error][:message]}")
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end
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response[:result]
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end
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def list_prompts(cursor: nil, request_id: nil)
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params = cursor ? { cursor: cursor } : nil
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request = build_request(Methods::PROMPTS_LIST, params, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to list prompts: #{response[:error][:message]}")
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end
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response[:result]
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end
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def get_prompt(name:, arguments: {}, request_id: nil)
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params = { name: name }
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params[:arguments] = arguments unless arguments.empty?
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request = build_request(Methods::PROMPTS_GET, params, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to get prompt '#{name}': #{response[:error][:message]}")
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end
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response[:result]
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end
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def list_resources(cursor: nil, request_id: nil)
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params = cursor ? { cursor: cursor } : nil
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request = build_request(Methods::RESOURCES_LIST, params, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to list resources: #{response[:error][:message]}")
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end
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response[:result]
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end
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def read_resource(uri:, request_id: nil)
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request = build_request(Methods::RESOURCES_READ, { uri: uri }, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to read resource '#{uri}': #{response[:error][:message]}")
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end
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response[:result]
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end
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def list_resource_templates(cursor: nil, request_id: nil)
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params = cursor ? { cursor: cursor } : nil
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request = build_request(Methods::RESOURCES_TEMPLATES_LIST, params, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to list resource templates: #{response[:error][:message]}")
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end
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response[:result]
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end
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def subscribe_resource(uri:, request_id: nil)
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request = build_request(Methods::RESOURCES_SUBSCRIBE, { uri: uri }, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to subscribe to resource '#{uri}': #{response[:error][:message]}")
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end
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response[:result]
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end
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def unsubscribe_resource(uri:, request_id: nil)
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request = build_request(Methods::RESOURCES_UNSUBSCRIBE, { uri: uri }, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to unsubscribe from resource '#{uri}': #{response[:error][:message]}")
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end
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response[:result]
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end
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def set_logging_level(level:, request_id: nil)
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request = build_request(Methods::LOGGING_SET_LEVEL, { level: level }, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to set logging level: #{response[:error][:message]}")
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end
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response[:result]
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end
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def complete(ref:, argument:, request_id: nil)
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params = {
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ref: ref,
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argument: argument,
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}
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request = build_request(Methods::COMPLETION_COMPLETE, params, request_id)
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response = @transport.send_request(request)
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if response[:error]
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raise ClientError.new("Failed to get completions: #{response[:error][:message]}")
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end
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response[:result]
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end
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private
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def build_request(method, params = nil, request_id = nil)
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request = {
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jsonrpc: "2.0",
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method: method,
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id: request_id.nil? ? next_request_id : request_id,
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}
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request[:params] = params if params
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request
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end
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def next_request_id
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@request_id += 1
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end
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end
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end

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