Customizable, no-code voice agent automation with GPT-4o

Retell AI 正在从零开始重塑呼叫中心。与其在传统呼叫脚本系统上做“加法”，他们打造了一个以 AI 为核心、无需编码的平台，可快速部署自然流畅的语音客服，能够回答问题、安排预约、处理各类日常事务——无需等待、无需手动脚本，也不需复杂工程投入。

这种被称为“语音自动化”的技术，可以让企业全天候即时接听来电，消除排队等待、降低运营成本，并提升客户满意度。

凭借对 OpenAI 模型发布时间的紧密跟踪和快速集成，Retell 能在数日内将新功能交付客户。正如联合创始人兼 CTO 张泽霞所说：“模型越强大，我们的平台就越出色。我们不仅扩展速度更快，也能用更简单的技术栈解决更复杂的问题。”

这一策略效果显著：使用 Retell 的团队报告呼叫处理成本平均降低高达 80%，而 Retell 各部署点的净推荐值（NPS）高达 90。

一、借力 GPT-4o，实现实时、近乎人类的对话体验
为了让对话更自然，Retell 需要一个超越固定脚本的 AI 方案，既能理解上下文、跟随逻辑，又能实时触发正确动作。评估多款大型语言模型后，OpenAI 凭借其精准性和性能脱颖而出。

“OpenAI 的模型在速度、可靠性和智能度上达到了最佳平衡。”张泽霞说，“我们测试函数调用时，GPT 系列不仅最准确，响应速度也最快。这种表现对真实对话至关重要。”

Retell 的语音客服通过函数调用来安排预约、识别潜在客户、处理行政事务等。在每种场景下，模型都需要在多轮对话中进行推理，并在恰当时机调用正确的 API。张泽霞补充道：“这填补了电话交流中的最后一块拼图。有了 GPT-4o，客服就像真人一样：倾听、思考、自然回应。”

二、选择 GPT-4o 和 GPT-4.1，兼顾速度与精准
GPT-4o 是个关键突破：它让 Retell 能在不依赖繁琐提示工程或硬编码逻辑的前提下，构建动态对话流程，例如预约安排、异议处理和细节确认。此前，团队要手动拼接指令、管理上下文窗口、写 3,000 字的提示；如今，客户只需在简单界面上设定目标、选择条件与动作，剩下的都交由模型完成。

“这类工作流通常需要大量手工逻辑、备用提示、外部记忆和 JSON 校验。”联合创始人兼 CEO 吴冰说，“以前我们要花数周时间搭建解决方案，而现在客户几天内就能上线。”

OpenAI 原生的函数调用接口也带来巨大优势。其他模型常常需要自定义方案或强制校验，而 GPT-4o 提供了更自然、可靠的接口，多轮函数调用成功率超过 70%，几乎是竞争产品的一倍，且无需特别提示，仅靠模型对函数描述的理解即可高效完成。

借助 GPT-4o，Retell 还快速推出一系列新功能：
· 通话后分析与结果评估
· 可配置的客服工作流，几乎无需提示工程
· 具有反驳能力和多槽位预约的动态对话流程

这一切都在仅 11 人的小团队中完成，并对客户开箱即用。借助 GPT-4o，Retell 能从想法迅速迈向面向生产的真实对话代理。

随着 OpenAI 持续发布新模型（包括 GPT-4.1），Retell 也在不断扩展客服能力。每一次升级，都为客户带来更灵敏的反应、更紧密的 CRM 集成和更智能的工作流，且在数日内迅速交付。

三、用 OpenAI 实现全生命周期的语音自动化
Retell 通过轻量化、模型原生的方案，覆盖了从接听到结果评估的全流程语音自动化。目前他们已见到显著成效：
· 呼叫处理成本最多降低 80%
· 全天候服务，CSAT（客户满意度）得分 85% 以上，媲美或超越人工客服
· 85–90% 的合格来电成功转接率
· 上线 16 个月内实现 1,400 万美元收入
· 月均增长率 25%

随着每次新模型的落地，如 GPT-4.1，Retell 都能解锁新功能：更高级的对话流程、智能转接/升级功能、更强大的拨号系统、更深度的 CRM 集成、实时分析、智能评分及 QA。所有功能都集成在直观易用的平台中，让团队无需额外运维，就能快速部署定制化语音代理。

张泽霞表示：“我们不仅在搭建客服代理，更在为未来的客户对话构建底层基础设施。”

Retell AI⁠ is rebuilding the call center from first principles. Instead of retrofitting legacy call scripting systems, they’ve created an AI-native, no-code platform that spins up natural-sounding voice agents that can answer questions, schedule appointments, and resolve administrative issues—no hold music, scripting, or heavy engineering required. 

This category of technology, known as voice automation, enables businesses to handle calls instantly, around the clock, while eliminating hold times, reducing operational costs, and improving customer satisfaction.

By closely tracking OpenAI model releases and integrating them quickly, Retell can deliver new capabilities to customers within days. As co-founder and CTO Zexia Zhang explains, “Because the models keep getting better, our platform keeps getting better. We’re not just scaling faster, we’re tackling more complex problems with a simpler stack.”

That approach is paying off: teams using Retell report up to 80% reductions in call handling costs, and Retell is seeing a high NPS of 90 across deployments. 

Unlocking real-time, human-like conversations with GPT‑4o 

To enable natural conversations, Retell needed an AI provider that could move beyond scripted exchanges, something that could understand context, follow logic, and trigger the right actions in real-time. After evaluating multiple LLMs, OpenAI stood out for its precision and performance. 

“OpenAI’s models strike the best balance of speed, reliability, and intelligence,” says Zhang. “When we tested function calling, GPT models were not only the most accurate, they were the fastest to respond. That level of performance is critical for real-world conversations.”

Retell voice agents use function calling to schedule appointments, qualify leads, and resolve administrative issues. In each case, the model needs to reason across multiple turns of conversation and invoke the right API at the right time. 

“It was the last missing piece of a great phone call,” Zhang adds. “With GPT‑4o, the agent finally acts like a human: it listens, reasons, and responds naturally.”

Hear Retell AI in action: natural-sounding voice, low latency, and near-instant responses.

Choosing GPT‑4o, GPT‑4.1 for precision at speed

GPT‑4o was a turning point: it enabled Retell to build dynamic conversation flows, like scheduling appointments, handling objections, and confirming details, without extensive prompt engineering or hardcoded logic. Instead of chaining together brittle instructions, manually managing context windows, or writing 3,000-token prompts for every use case, Retell’s customers can now define behavior through a simple UI. They write a high-level goal, select a few conditions or actions, and the model handles the rest. 

“Typically, these workflows require lots of manual logic, fallback prompts, external memory, JSON enforcement,” says Bing Wu, Retell co-founder and CEO. “We used to spend weeks building workarounds. Now customers can go live in days.”

OpenAI’s native function calling interface was another unlock. Competing models often required pieced-together solutions or custom schema enforcement. GPT‑4o provided a more natural, reliable interface and achieved a 70%+ success rate in multi-turn function calling, nearly double what Retell saw from alternatives, without careful prompting, relying solely on the model’s understanding of the function descriptions.

Retell also used GPT‑4o to launch entire new capabilities like:

• Post-call analysis and outcome evaluation
• Configurable agent workflows with minimal prompt engineering
• Dynamic conversation flows like rebuttals and multi-slot appointment booking

All of this was built and shipped with a lean team of 11 and made accessible to Retell’s customers without requiring complex setup. With GPT‑4o, Retell moved quickly from idea to production-ready agents that could handle real-world conversations.

That speed hasn’t let up. Retell continues to integrate OpenAI’s newest models, including GPT‑4.1, to extend what their agents can do. Each release brings new opportunities: more responsive behavior, tighter CRM integrations, and smarter workflows, all delivered to customers in a matter of days.

Automating the full customer conversation lifecycle with OpenAI

Retell’s lean, model-native approach is now powering the full lifecycle of voice automation, from answering the call to measuring its outcome. And they’re seeing real results: 

• Up to 80% reduction in call handling costs 
• 24/7 availability with CSAT scores of 85%+, matching or exceeding human agents
• 85-90% success rate in qualified call transfers
• $14M in revenue within 16 months of launching 
• 25% average month-over-month growth

With every new model release, like GPT‑4.1, Retell unlocks new functionality like more advanced conversation flows, intelligent warm transfers or escalations to human agents, a more powerful dialer, deeper CRM integrations, real-time analytics, smarter call scoring and quality assurance (QA). All of it is built into an intuitive platform that lets teams launch custom agents quickly and without adding operational overhead.

“We’re not just building agents anymore,” says Zhang. “We’re building infrastructure for the future of customer conversations.”

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