Comparing Sierra AI and Vapi? Both are AI Agents & Chatbots and Voice & Phone AI tools in the directory, which is why buyers put them on the same shortlist. Below is a side-by-side look at how they price, what they integrate with, and when each is the better fit, so you can pick on the facts rather than either vendor's own sales page.
| Attribute | Sierra AI | Vapi |
|---|---|---|
| Pricing | Per resolution · Custom | Paid · $0.05/min + provider costs |
| Founded | 2023 | 2020 |
| Categories | AI Agents & Chatbots Enterprise Voice & Phone AI | AI Agents & Chatbots Voice & Phone AI |
| Integrations | Salesforce Zendesk Shopify Twilio Stripe Snowflake | Twilio Vonage Telnyx Deepgram ElevenLabs PlayHT OpenAI Anthropic |
Sierra builds conversational AI agents for the enterprise, and it arrived with about as much star power as a startup can carry. It was founded in 2023 by Bret Taylor and Clay Bavor, and if those names ring a bell it is because Taylor co-created Google Maps, served as CTO of Facebook and co-CEO of Salesforce, and currently chairs the board of OpenAI, while Bavor spent eighteen years at Google leading its virtual and augmented reality work. Company lore says the whole thing was hatched over a grilled branzino lunch in Palo Alto.
The product lives up to the pedigree. From a single build, Sierra deploys a branded agent across chat, voice, email, SMS, and even ChatGPT, following your policies, adopting your brand's voice, and escalating gracefully when a conversation gets thorny. Its voice agents are a standout: they hold natural, low-latency conversations, read sentiment, and can even take a credit card or ACH payment over the phone in one uninterrupted call, with no clumsy handoff to a separate system.
Under the hood sits Agent OS, a platform for building, testing, and supervising agents, with tooling to run voice simulations and rehearse behavior before anything reaches a real customer. Pricing is outcome-based, tied to conversations or successful resolutions and wrapped in multi-year enterprise contracts, so Sierra is aimed at large brands rather than weekend experimenters. Reported customers include SoFi, Ramp, and Brex, and the company says its agents already serve a meaningful slice of the Fortune 50.
Sierra's fundraising has kept pace with its towering ambition, vaulting the company into the rarefied tier of the most valuable AI startups in barely two years. For enterprises that want polished, on-brand agents across every channel and are willing to invest the time and budget to do it properly, Sierra is a genuine marquee choice.
Read the full Sierra AI listing → · See Sierra AI alternatives →
Vapi is a developer platform for voice AI agents. Rather than selling a finished support bot, it sells the orchestration layer: an API and SDKs that wire together speech-to-text (Deepgram and others), any major LLM (OpenAI, Anthropic), text-to-speech (ElevenLabs, PlayHT, Cartesia), and telephony (Twilio, Vonage, Telnyx) into a low latency phone agent. Support teams meet Vapi indirectly, as the engine behind custom-built inbound support lines, appointment desks, and agencies' white label voice products.
Founders Jordan Dearsley and Nikhil Gupta went through Y Combinator in 2021 with a productivity app called Superpowered, then pivoted to voice infrastructure in 2023 after Dearsley built himself an AI phone bot to think out loud with. It worked: Vapi reports over a million developers and a billion calls handled. It raised a $20 million Series A led by Bessemer in December 2024, then a $50 million Series B in May 2026 at a $500 million valuation, roughly $72 million total. Amazon chose Vapi for its Ring division after evaluating over 40 rivals.
Pricing starts at $0.05 per minute for the platform itself, with SMS at $0.005 per message. Provider costs (speech, LLM, voice, telephony) are passed through at cost, or drop to zero if you bring your own API keys. Realistic all in costs run $0.07 to $0.25 per minute. Ten concurrent calls are included, extra lines cost $10 monthly, and compliance add-ons are priced like enterprise software: HIPAA at $2,000 monthly, zero data retention at $1,000 monthly.
Choose Vapi if you have engineers and want maximum control over every layer of a support voice agent, with the freedom to swap providers as models improve. Skip it if nobody on your team writes code, or you want a vendor accountable for resolution rates rather than infrastructure.
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