Class: Clacky::Mcp::Client

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

Overview

JSON-RPC 2.0 client for a single MCP server.

Lifecycle: open transport on #start, send ‘initialize` handshake, then any number of `tools/list` / `tools/call` requests, then #stop closes the transport. Transport is selected by spec: “stdio” (default) or “http”.

Defined Under Namespace

Classes: McpError, ProtocolError

Constant Summary collapse

TransportError = 
Mcp::Transport::TransportError
DEFAULT_TIMEOUT = 
30
INIT_TIMEOUT = 
15
PROTOCOL_VERSION = 
"2024-11-05"

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(name:, transport: nil, command: nil, args: [], env: {}, cwd: nil) ⇒ Client

Returns a new instance of Client.



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# File 'lib/clacky/mcp/client.rb', line 61

def initialize(name:, transport: nil, command: nil, args: [], env: {}, cwd: nil)
  @name = name
  @transport = transport || StdioTransport.new(name: name, command: command, args: args, env: env, cwd: cwd)

  @pending = {}
  @next_id = 0
  @lock    = Monitor.new
  @started = false

  @tools       = []
  @server_info = nil
  @started_at  = nil
  @last_used_at = nil

  @transport.on_message do |msg|
    if msg["__transport_closed__"]
      @lock.synchronize do
        @pending.each_value { |q| q.push({ "error" => { "code" => -32000, "message" => "transport closed" } }) }
        @pending.clear
      end
      next
    end

    id = msg["id"]
    if id && (queue = @lock.synchronize { @pending.delete(id) })
      queue.push(msg)
    end
  end
end

Instance Attribute Details

#last_used_at ⇒ Object (readonly)

Returns the value of attribute last_used_at.



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# File 'lib/clacky/mcp/client.rb', line 27

def last_used_at
  @last_used_at
end

#name ⇒ Object (readonly)

Returns the value of attribute name.



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# File 'lib/clacky/mcp/client.rb', line 27

def name
  @name
end

#server_info ⇒ Object (readonly)

Returns the value of attribute server_info.



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# File 'lib/clacky/mcp/client.rb', line 27

def server_info
  @server_info
end

#started_at ⇒ Object (readonly)

Returns the value of attribute started_at.



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# File 'lib/clacky/mcp/client.rb', line 27

def started_at
  @started_at
end

#tools ⇒ Object (readonly)

Returns the value of attribute tools.



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# File 'lib/clacky/mcp/client.rb', line 27

def tools
  @tools
end

Class Method Details

.from_spec(name, spec) ⇒ Object

Build a Client from an mcp.json spec hash. Recognized fields:

stdio: command (required), args, env, cwd
http:  type: "http", url (required), headers



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# File 'lib/clacky/mcp/client.rb', line 33

def self.from_spec(name, spec)
  type = (spec["type"] || (spec["url"] ? "http" : "stdio")).to_s
  case type
  when "stdio"
    new(
      name:    name,
      transport: StdioTransport.new(
        name:    name,
        command: spec["command"],
        args:    Array(spec["args"]),
        env:     spec["env"] || {},
        cwd:     spec["cwd"]
      )
    )
  when "http", "streamable-http"
    new(
      name:    name,
      transport: HttpTransport.new(
        name:    name,
        url:     spec["url"],
        headers: spec["headers"] || {}
      )
    )
  else
    raise McpError, "unsupported MCP transport type '#{type}' for server '#{name}'"
  end
end

Instance Method Details

#call_tool(tool_name, arguments = {}) ⇒ Object 



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# File 'lib/clacky/mcp/client.rb', line 137

def call_tool(tool_name, arguments = {})
  ensure_started!
  @last_used_at = Time.now
  request("tools/call", { name: tool_name, arguments: arguments || {} })
end

#start ⇒ Object 



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# File 'lib/clacky/mcp/client.rb', line 95

def start
  already_started = false
  @lock.synchronize do
    if @started
      already_started = true
    else
      @transport.start
    end
  end
  return self if already_started

  handshake
  fetch_tools

  @lock.synchronize do
    @started = true
    @started_at = Time.now
    @last_used_at = @started_at
  end
  self
end

#started? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/clacky/mcp/client.rb', line 91

def started?
  @started
end

#stderr_tail(bytes: 4096) ⇒ Object 



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# File 'lib/clacky/mcp/client.rb', line 143

def stderr_tail(bytes: 4096)
  @transport.stderr_tail(bytes: bytes)
end

#stop ⇒ Object 



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# File 'lib/clacky/mcp/client.rb', line 117

def stop
  @lock.synchronize do
    @transport.stop rescue nil
    @started = false
  end
end

#tool_definitions ⇒ Object 



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# File 'lib/clacky/mcp/client.rb', line 124

def tool_definitions
  @tools.map do |t|
    {
      type: "function",
      function: {
        name: t["name"],
        description: t["description"].to_s,
        parameters: t["inputSchema"] || { type: "object", properties: {} }
      }
    }
  end
end