Module: ActionMCP::Server::Capabilities

Included in:
TransportHandler
Defined in:
lib/action_mcp/server/capabilities.rb

Instance Method Summary collapse

Instance Method Details

#send_capabilities(request_id, params = {}) ⇒ Hash

Handles the ‘initialize’ request. Validates parameters, checks protocol version, stores client info, initializes the session, and returns the server capabilities payload or an error payload.

Parameters:

  • request_id (String, Integer) —

    The JSON-RPC request ID.

  • params (Hash) (defaults to: {}) —

    The JSON-RPC parameters.

Returns:

  • (Hash) —

    A hash representing the JSON-RPC response (success or error).



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# File 'lib/action_mcp/server/capabilities.rb', line 12

def send_capabilities(request_id, params = {})
  client_protocol_version = params["protocolVersion"]
  client_info = params["clientInfo"]
  client_capabilities = params["capabilities"]
  session_id = params["sessionId"]

  unless client_protocol_version.is_a?(String) && client_protocol_version.present?
    return send_jsonrpc_error(request_id, :invalid_params, "Missing or invalid 'protocolVersion'")
  end

  unless ActionMCP::SUPPORTED_VERSIONS.include?(client_protocol_version)
    error_message = "Unsupported protocol version. Client requested '#{client_protocol_version}' but server supports #{ActionMCP::SUPPORTED_VERSIONS.join(', ')}"
    error_data = {
      supported: ActionMCP::SUPPORTED_VERSIONS,
      requested: client_protocol_version
    }
    return send_jsonrpc_error(request_id, :invalid_params, error_message, error_data)
  end

  unless client_info.is_a?(Hash)
    return send_jsonrpc_error(request_id, :invalid_params, "Missing or invalid 'clientInfo'")
  end
  unless client_capabilities.is_a?(Hash)
    return send_jsonrpc_error(request_id, :invalid_params, "Missing or invalid 'capabilities'")
  end

  # Handle session resumption if sessionId provided
  if session_id
    existing_session = ActionMCP::Session.find_by(id: session_id)
    if existing_session&.initialized?
      # Resume existing session - update transport reference
      transport.instance_variable_set(:@session, existing_session)

      # Return existing session info
      capabilities_payload = existing_session.server_capabilities_payload
      capabilities_payload[:protocolVersion] = client_protocol_version
      return send_jsonrpc_response(request_id, result: capabilities_payload)
    end
  end

  # Create new session if not resuming
  session.store_client_info(client_info)
  session.store_client_capabilities(client_capabilities)
  session.set_protocol_version(client_protocol_version)

  unless session.initialize!
    return send_jsonrpc_error(request_id, :internal_error, "Failed to initialize session")
  end

  capabilities_payload = session.server_capabilities_payload
  capabilities_payload[:protocolVersion] = client_protocol_version

  send_jsonrpc_response(request_id, result: capabilities_payload)
end