Class: Phronomy::Tool::McpTool::StdioTransport

Inherits:
Object
  • Object
show all
Defined in:
lib/phronomy/tool/mcp_tool.rb

Overview

Minimal stdio transport implementing a subset of the MCP JSON-RPC protocol. Spawns the server command as a child process and communicates line-by-line.

Instance Method Summary collapse

Constructor Details

#initialize(command) ⇒ StdioTransport

Returns a new instance of StdioTransport.



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# File 'lib/phronomy/tool/mcp_tool.rb', line 84

def initialize(command)
  # Split the command string into an argv array so that Open3 executes
  # it directly without going through the shell, preventing injection.
  @command = Shellwords.split(command)
end

Instance Method Details

#call_tool(tool_name, args) ⇒ Object

Call a tool on the MCP server using the tools/call method.

Parameters:

  • tool_name (String)
  • args (Hash)

Returns:

  • (Object) —

    the tool result



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# File 'lib/phronomy/tool/mcp_tool.rb', line 109

def call_tool(tool_name, args)
  response = rpc_call("tools/call", {name: tool_name, arguments: args})
  content = response.dig("result", "content")

  # MCP content is an array of content blocks; extract text blocks.
  if content.is_a?(Array)
    texts = content.select { |c| c["type"] == "text" }.map { |c| c["text"] }
    (texts.length == 1) ? texts.first : texts
  else
    content
  end
end

#fetch_tool(tool_name) ⇒ Hash

Retrieve the tool definition from the server using the MCP tools/list method.

Parameters:

  • tool_name (String)

Returns:

  • (Hash) —

    { description:, parameters: }

Raises:

  • (ArgumentError) 


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# File 'lib/phronomy/tool/mcp_tool.rb', line 93

def fetch_tool(tool_name)
  response = rpc_call("tools/list", {})
  tools = response.dig("result", "tools") || []
  defn = tools.find { |t| t["name"] == tool_name }
  raise ArgumentError, "Tool #{tool_name.inspect} not found on MCP server #{@command.inspect}" unless defn

  {
    description: defn["description"],
    parameters: parse_schema_params(defn.dig("inputSchema", "properties") || {})
  }
end