How do I use a Union type as an action argument?

defmodule Insi.Subscriptions.SubscriptionPlan do
  use Ash.Resource...

  attributes do
    ...
    attribute :features, {:array, Feature} do
      public? true
      default []
    end
  end
  actions do
    ...
    update :add_features do
      argument :features, {:array, Feature}
      manual AddFeatures
    end
  end

  code_interface do
    define :add_features, args: [:features]
  end
end

defmodule Insi.Subscriptions.Feature do
  use Ash.Type.NewType,
    subtype_of: :union,
    constraints: [
      types: [
        installations: [
          tag: :type,
          tag_value: :installations,
          type: :integer
          # constraints: [min: 0]
        ],
    ...
end

SubscriptionPlan.add_features([%Ash.Union{type: :installations, value: 1}]
SubscriptionPlan.add_features([%Ash.Union{type: :installations, content: 1}]
SubscriptionPlan.add_features([%{type: :installations, value: 1}]
SubscriptionPlan.add_features([%{type: :installations, content: 1}]

%Ash.Error.Changes.InvalidArgument{field: :features, message: "is not a map", value: [%Ash.Union{value: 1, type: :installations}]...}