Why does the assistant sound like a robot?

It is rarely the voice. It is the timing around it.

It answers too quickly. A person pauses briefly before answering. If the assistant answers the same second you stop talking, it feels wrong, even when the words are right.

It interrupts. If patience is set too low, it starts talking every time there is half a second of silence — and people pause in the middle of a sentence when they are thinking.

It says too much. Long answers sound like a reading. Write the instruction so it answers briefly and asks one question at a time.

Try turning patience up first. That is the setting that most often makes the whole difference.

Where to adjust

Assistants → select the assistant → How it sounds. There you will find Interruption sensitivity and Waiting for a reply — those are the two that are most often the problem. Set them both to "Patient" and call again.

If that does not help, the instruction is too long. See How to write a good instruction.