Time to first token: the latency metric that decides voice agents

Time to first token (TTFT) is a crucial metric for evaluating the responsiveness of voice agents, measuring the elapsed time from when a user stops speaking to when the system produces the first usable output. Unlike word error rate (WER) or average latency, TTFT captures the immediate experience of a conversation, as it determines the responsiveness that users perceive. The article explains that TTFT is essential because it dictates how quickly a voice agent can respond, with the end-to-end pipeline involving speech-to-text (STT), language model (LLM), and text-to-speech (TTS) stages. Accurate measurement involves recording realistic audio clips, marking the end of user speech and the receipt of the first token, and reporting percentiles to understand typical and tail-end experiences. The piece emphasizes that while WER addresses accuracy, TTFT is pivotal for ensuring a voice agent feels alive and responsive, making it a vital consideration for speech-to-text evaluations.

Use this post, company, and trend context to find content marketing opportunities, perform competitive analysis, or address product feature gaps via the Plushcap MCP server or the Plushcap API.