CarMax routes 100% of its calls through Sierra's AI, but the sale itself stays human
CarMax routes every inbound call through Sierra voice agents and keeps the sale with associates. Sierra and Meta's new protocol wants to hand that last step to agents. Sierra sells to both camps.
Vincent Jiang · 3 min read
An AI voice picks up every call
Call a CarMax store asking about hours, or whether a car is still on the lot, and a Sierra voice agent answers first, asks clarifying questions, and hands the rest to an associate 1. On the September 29 earnings call, chief executive Keith Barr said CarMax had "scaled AI voice technology to 100% of both inbound store and customer experience center calls" 2.
The agents went live in May 45. CarMax reports more calls resolved and fewer left unresolved since launch, figures it has not published 4.
The company is now extending them to schedule appraisals, browsing visits and test drives 14. More than 45,000 vehicles already sit in its ChatGPT app 1.
Sierra is paid for the call, not the car
Sierra's disclosed business is conversations, not transactions: agents on its platform handle billions of interactions, its annual recurring revenue passed $150 million in February, and it raised $950 million in May at a valuation above $15 billion 6. Nothing published ties its income to the close.
The CarMax quarter Sierra now helps defend ran to $7.9 billion in revenue, up 19.5%, and net earnings of $165.3 million, up 73.3% 3. Whether the AI answering its phones is bending that cost line is the question for the comprehensive investor strategy CarMax has promised for November 2.
The merchants keeping the close human
On October 6, 2026, Sierra, the same vendor answering CarMax's phones, and Meta published the Personal Agent Protocol with Shopify, Stripe, Walmart and others 7. Its roadmap includes payment extensions that would let an agent complete a purchase without sharing card details 7.
Meta's line for hesitant brands: "Turning away a personal agent means turning away the customer behind it" 7. Shopify says Muse will be able to buy from every merchant on its platform 8. Barr's answer is that every used car is an individual SKU, and buyers want to see, touch and test drive before they sign 1.
The retail record sides with him so far: Tapestry lets agents browse but not buy, Kohl's blocks agent purchases, eBay barred agents in January, and Amazon blocked Muse outright 8. Only 3% of US adults would trust an agent to complete a purchase, an NMI survey found, and a third of active AI users told VML they would never let one buy 8.
The number nobody has printed
The agent-closers still own the momentum: Muse counts millions of US users 9, and Bret Taylor calls the moment "kind of chaos until such a standard exists" 9, though Amazon, OpenAI and Anthropic have stayed out 910. Sierra plans to publish the v0.1 specification later this month 7, and CarMax promises investors a full strategy in November 2. The number neither side prints is whether call deflection reaches cost-to-serve before the human sales floor thins. Sierra gets paid either way.
Deepdive
AI-generated from this story and its cited sources. Not investment advice.
