We sent one client email to 5 AI models.

Here's an experiment you can steal. We wrote one realistic client email — the kind that lands in your inbox every week — and fired it at six AI models at the exact same second, through one API. Then we graded the replies against a four-point checklist.

Most CX platforms do not own the voice. They orchestrate a workflow, then call a third party for speech and transcription. Every hop adds latency, cost, and another vendor to manage.

ElevenAgents is the opposite. They make the voice models the market builds on, and ElevenAgents puts full orchestration on top. Voice, transcription, text-based chat, and reasoning run in one vertically integrated pipeline, so responses come back in <400 milliseconds and sound human, not synthetic.

Plus, you keep full control. Plug in any LLM, integrate tools, webhooks, and MCP servers, and ground responses in your knowledge base. Get an agent live in minutes, then A/B test with Experiments, enforce Guardrails, and version every change.

The payoff: more human conversations, lower latency, and far less time stitching infrastructure together. You build on the models you already trust. Pricing is transparent and flat at $0.08 per minute.

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The email, from a client named Marcus, buried four requirements in five casual sentences: move Thursday's call, he flies to London Sunday for two weeks, revised proposal with new pricing before he leaves, and copy his colleague Dana on everything while he's gone.

The trap is the scheduling. A good reply doesn't offer "alternative times" — it notices the reschedule has to happen before Sunday, because next week Marcus is five time zones away.

TLDR: The frontier models (Claude Opus, Claude Sonnet, GPT-5.4) all caught everything, including the buried deadline. The budget models got 3 of 4 — and the cheapest one didn't just miss a detail. It invented one: a scheduling conflict you never had, stated as fact, in a reply sent under your name. We reran it to be sure. Three fabrications in four runs.

— The part that should worry you —

The fabrication wasn't dramatic. It was one plausible little sentence — "Thursday at 2 doesn't work for me either" — that your client would simply believe. Not a fake court case in a legal brief. A fake fact in a routine email. That's the failure mode nobody's demo shows you.

The pattern held every time information was missing: the frontier models asked for it. The budget model asserted it.

— And the price? Basically irrelevant —

All five replies together cost 1.2 cents. The spread between the cheapest and priciest model was two-thirds of a penny. You're not choosing on cost anymore. You're choosing on judgment.

— Keep reading on the site —

The full piece has the parts you'll actually use:

Oh — and the fifth model? It never answered at all. The reason is the most human failure in tech, and it's in the article.

— The AI Super Simplified team