I’m working with Vapi tools where vapi sends a tool-call request to my server, but the backend execution might take ~30seconds. When the tool is triggered, the conversation stays silent until the tool result is returned, which isn’t a great. Is there a way to immediately acknowledge the tool call (e.g. “I’m working on this, it may take a moment”) keep the call active (avoid silence) then send the final result once the long-running task completes? I’ve set async: true on tools, but it doesn’t seem to work, and the assistant often goes silent.