Convenience macro for defining function-backed tools with JSON schemas.

Usage:

defmodule MyTool do
  use Codex.FunctionTool,
    name: "add",
    description: "Adds numbers",
    parameters: %{left: :number, right: :number},
    handler: fn %{"left" => left, "right" => right}, _ctx ->
      {:ok, %{"sum" => left + right}}
    end
end

Options:

• :name - tool name (defaults to module name)
• :description - human-friendly description
• :parameters - map of parameter names to type atoms or schema maps
• :required - list of required parameter names (defaults to all)
• :schema - explicit JSON schema (overrides generated schema)
• :strict? - when true sets "additionalProperties": false (default)
• :handler - function to invoke (falls back to handle/2 or handle/1)
• :enabled? - predicate to gate invocation (arity 1 or 2)
• :on_error - fallback handler invoked with the error (arity 2 or 3)