How to send a response that is different from the default one?

In my Ash resource, I’ve defined an action which returns a map like below:

actions do
  action :get_presigned_url, :map do
    run fn _, _ ->
      ...
      {:ok, %{filename: filename, presigned_url: presigned_url}}
    end
  end
end

But the above code returns an error saying that

an exception was raised:
    ** (Spark.Error.DslError) [MyApp.Domain]
json_api -> routes -> get -> get_presigned_url_for_audio:
  Invalid return type for generic action used in get route.

Expected type `:struct`
Expected constraints: instance_of: Dharana.Resource

Got type: Ash.Type.Map
Got constraints: []

Is it possible to do what I’m trying to do? I’m looking for a way to only send the map as the response through Ash