Create a New MCP Tool

Creates a new FastMcp::Tool that the AI agent (OpenFang) can use via MCP.

Steps

1. •Create the tool file at fang/tools/<tool_name>_tool.rb
2. •Use this template:

# frozen_string_literal: true

module Fang
  module Tools
    class <ToolName>Tool < FastMcp::Tool
      tool_name '<tool_name>'
      description '<What this tool does — be specific, the agent reads this>'

      arguments do
        required(:<arg>).filled(:string).description('<Argument description>')
        optional(:<opt>).filled(:string).description('<Optional argument>')
      end

      def call(<arg>:, <opt>: nil)
        # All Fang:: models are available here (Conversation, Message, Page, etc.)
        # Return a hash — the agent receives this as the tool result

        { success: true, result: 'done' }
      rescue => e
        Fang.logger.error "#{self.class.name} failed: #{e.message}"
        { success: false, error: e.message }
      end
    end
  end
end

1. •No registration needed — tools are auto-discovered via ObjectSpace scanning in fang/mcp_server.rb
2. •Restart the server (./openfang.rb server) to pick up the new tool
3. •Verify: ./openfang.rb console → check tool is listed

Argument Types

FastMcp uses dry-schema. Common types:

• •.filled(:string) — non-empty string
• •.filled(:integer) — integer
• •.filled(:bool) — boolean
• •.filled(:hash) — hash/object
• •.filled(:array) — array

Broadcasting to UI

If your tool needs to push updates to the web UI in real-time:

turbo_html = "<turbo-stream action=\"append\" target=\"some-target\"><template>#{html}</template></turbo-stream>"
Fang::Web::TurboBroadcast.broadcast('channel-name', turbo_html)

Conventions

• •File: fang/tools/<snake_case>_tool.rb
• •Class: Fang::Tools::<PascalCase>Tool
• •tool_name: 'snake_case' (this is what the agent calls)
• •Always return { success: true/false, ... } hashes
• •Log operations via Fang.logger.info/error
• •Also update workspace/CLAUDE.md tool table so OpenFang knows about the new tool