The Hidden Cost of Ignoring Tokens in Voice Agent Design.
Many people new to voice agents ignore token usage because the costs and performance effects are invisible at first and only show up later in the live environment.
And when the cost spike they are forced to re-design the entire voice agent from scratch.
If a voice agent is built with no token or latency budget, fixes later usually require shrinking the global prompt, restructuring state prompts, pruning tools, redesigning the knowledge base, and tightening conversation flow, which is closer to a rebuild than a minor optimization.
Because prompt structure, KB design, and function schemas are all interdependent.
You cannot just “trim a few lines” once you hit high usage and high cost; you often have to re-architect the agent around token efficiency, introducing shorter prompts, better chunking, selective history, and more disciplined retrieval.
Build Voice Agents with token and latency budget.
The entire voice agent needs to be designed with token limits and latency in mind, or it will cost significantly more per minute and feel slower on live calls.
Retell’s pricing increases as token usage grows, and longer contexts also introduce extra processing time, which is very noticeable in real‑time voice.