One option could be for the main apps like WhatsApp to have defined custom actions, which are almost like an API to the service. I think the interplay between LLM and automation scripts will succeed here:

Agent call 1: Send WhatsApp message (to=Magnus, text=hi) Inside, you open WhatsApp and search for Magnus (without LLM)

Agent call 2: Select contact from all possible Magnus contacts Script 3: Type the message and click send

So in total, 2 calls - with Gemini, you could already achieve this in 10-15 seconds.