What is a voice AI agent? (And what it can actually finish)

What happens on a call

Every turn of a phone call runs the same four steps. The agent turns what the caller said into text, works out what to do next, looks something up in your booking system or customer records, then speaks back. All four have to finish inside the length of a natural pause, roughly 300 milliseconds. Past about 500, callers repeat themselves or talk over it.

The hard part is knowing when the caller has stopped talking. Cheap setups wait for silence and nothing else, so they cut people off mid-sentence or sit there saying nothing for 30 seconds. LiveKit released a turn detection model that reads the words alongside the silence, cutting unintended interruptions by 85%. Ask any vendor how theirs decides a caller is finished.

The number vendors quote, and the one to ask for

Vendors sell containment, the share of calls that never reach a person. A call counts as contained when the caller hangs up, including in frustration. Resolution, where the problem actually got fixed, runs lower. Password resets resolve at 80-95%. Billing complaints resolve at 10-25%. A blended 45-60% across the calls you send it is a good result, not a disappointing one.

When one is worth setting up

Start with one call type that is repetitive and already scripted. Per-minute prices look small (ElevenLabs charges $0.08 a minute for its agents, Vapi charges $0.05 for hosting alone), but the voice, the language model and the phone line are billed on top, so ask for the all-in figure. Give it 90 days: the first four weeks always run below target while someone listens back to failed calls and fixes gaps. If your busiest call type needs judgement, keep it with people.