Sierra is an AI agent platform for large consumer brands. It suits companies with high voice and messaging volume that want to pay for outcomes rather than seats. Small teams cannot try it, because Sierra has no public price, no trial, and no sign-up page.
iShort answer
This review scores Sierra 4.3 out of 5. G2 users rate it 4.5 from 128 reviews. Its agents work in chat, messaging apps, email, and voice. Voice covers 55+ languages, and agents are built from your existing procedures.
The limits are cost and access. Sierra publishes no price and sells through a contact form. Healthcare buyers should also confirm BAA terms directly, since no public page states them.
Key takeaways
| Aspect | Verdict |
|---|---|
| Best for | Large consumer brands with high voice and messaging volume |
| Pricing | Not published. Outcome-based contracts, with transfers to a person typically free |
| Biggest strength | Voice in 55+ languages, plus agents built from SOPs and transcripts |
| Biggest limitation | No price, no trial, and a sales-led rollout |
| G2 rating | 4.5 out of 5 from 128 reviews |
| Better fit for small teams | SiteGPT, from $39 a month billed yearly |
What to know before you fill in Sierra's contact form.
What it is
A platform that builds AI agents for chat, voice, and email and connects them to the systems they need to act in.
Who buys it
Enterprises. Sierra's funding announcement reported that over 40% of the Fortune 50 are customers.
How it charges
Per outcome, such as a resolved conversation or a saved cancellation. No rates are published.
What to confirm
BAA terms if you handle patient data. HIPAA is listed on the trust center, but the terms are not public.
What is Sierra AI?
Sierra is a conversational AI platform that builds AI agents for customer experience. Bret Taylor and Clay Bavor founded it after meeting at Google. Taylor was co-CEO of Salesforce and chairs OpenAI's board. Bavor spent 18 years at Google, where he led Google Labs.
On 4 May 2026 Sierra raised $950 million led by Tiger Global and GV, at a post-money valuation of over $15 billion. TechCrunch reported annual recurring revenue of $150 million as of early February 2026. The same report said over 40% of Fortune 50 companies use Sierra.
Its customer list includes SoFi, Rocket Mortgage, Vanguard, Hyatt, Wayfair, Discord, and Sutter Health. Chime appears as a customer of both Sierra and Decagon, its closest competitor.
Sierra's products and channels
Building the agent
Sierra gives three kinds of teams a way to build.
Agent Studio is the no-code builder. It turns existing operating procedures into agent journeys and includes AI evaluations, regression tests, and simulated voice calls. Sierra says it has more than 40 pre-built integrations but does not name them on the page.
The Agent SDK is for developers. It covers goals and guardrails, reusable skills, secure actions, and handoff to a contact center.
Ghostwriter, launched on 25 March 2026, builds the agent for you. You hand it SOPs, call transcripts, process documents, whiteboard photos, or audio recordings. It returns a production-ready agent across voice, chat, and email.
Channels
Sierra agents run on a website, in a mobile app, and over WhatsApp, Apple Business Chat, SMS, and email. Voice agents take and place calls in more than 55 languages and switch language mid-call. Companies can also publish an agent inside ChatGPT.
Voice Personas, released on 7 August 2026, let you set an agent's voice and personality separately from what it does. Sierra says pairing a natural voice with a persona raised one agent's resolution rate by almost 50%. It did not name the customer.
For phone systems, Five9 lists Sierra as an accredited AI provider connected over SIP. Five9 does not resell it, so you still buy from Sierra.
Long-running work with Horizon
Horizon, announced on 16 July 2026, is for goals that take days or weeks. Sierra's examples are originating a loan and getting prior authorization for a medical procedure. The agent coordinates inbound and outbound contact until the job is done. Sierra has not said whether Horizon is generally available.
Helping human agents and measuring results
Live Assist brings the AI agent to human reps with real-time guidance, drafted replies, and one-click actions. Insights handles reporting and experiments, and Explorer answers analytics questions asked in plain language.
Sierra wraps its models in what it calls supervisor models. These check responses for hallucinations, security issues, and abuse, and they block topics you mark as off limits.
Sierra uses forward-deployed engineers who tune agents for each customer, according to TechCrunch. The general shift from answering to acting is covered in AI agent vs chatbot.
How Sierra prices its agents
Sierra publishes no prices. Its pricing page returns a 404 and new buyers go through a contact form.
Sierra's model is outcome-based. Its December 2024 post says customers pay when the agent achieves an agreed outcome. Examples include a resolved conversation, a saved cancellation, an upsell, or a cross-sell. Bret Taylor has said a conversation transferred to a person is free, as quoted by Salesforce Ben.
| Outcome | Charged? |
|---|---|
| Agent resolves the conversation | Yes |
| Agent saves a cancellation or closes an upsell | Yes, if written into the contract |
| Conversation transferred to a person | Typically no |
Third parties estimate the cost. Quiq, a competitor, reports about $150,000 a year, with implementation starting around $50,000. AI Agent Square puts larger programs at $350,000 to $750,000 a year. None of these figures comes from Sierra.
Customer results Sierra publishes
Sierra's case studies give specific numbers. They measure different things, so read each one on its own terms.
80%
Resolution rate at Airtable, about the workload of 95 full-time agents
50% to 70%+
Resolution rate increase at Chime
+33
NPS points at SoFi for chat-contained conversations
73%
Troubleshooting cases resolved without a person at Singtel in the first 6 weeks
4x
Higher conversion at Rocket Mortgage when clients use AI chat
4 weeks
Time for Airtable to launch on chat, with email 7 days later
Rocket Mortgage runs more than 400,000 successful chat conversations and over 1 million outbound dials a month on Sierra. Singtel went live in under 10 weeks. All figures come from Sierra's customer stories.
Pros and cons
Pros
- Voice agents in 55+ languages, with inbound and outbound calling
- Ghostwriter builds agents from SOPs, transcripts, and recordings
- Outcome pricing, with transfers to a person typically not charged
- Trust center lists FedRAMP High, PCI DSS 4.0.1, ISO 42001, and HIPAA
- 4.5 out of 5 on G2 from 128 reviews
- Published results at Airtable, SoFi, Chime, and Rocket Mortgage
Cons
- No public pricing, and third-party estimates start around $150,000 a year
- No trial, no free plan, and no sign-up page
- Relies on Sierra's own engineers to tune agents, per TechCrunch
- Integrations beyond a count of 40+ are not named publicly
- BAA terms are not published
What G2 reviewers say
4.5/5·G2(128)Sierra holds 4.5 out of 5 on G2 from 128 reviews, read on 14 September 2026. Ninety are five stars, 36 are four stars, and 2 are three stars. Reviewers put the average time to implement at 1 month.
G2's summary says users praise natural conversations and faster responses. It says the agent can struggle with complex requests and sometimes needs a person to step in. The most-cited pros are ease of use and efficiency. The most-cited cons are cost.
One August 2026 reviewer liked how quickly a custom knowledge base was set up. The same reviewer said changes for edge cases sometimes meant going back to Sierra's team.
Security and compliance
Sierra's trust center lists a long set of frameworks.
| Framework | Status on the trust center |
|---|---|
| SOC 2 Type II | 2026 audit report, on request |
| HIPAA | 2026 HIPAA audit report, on request |
| PCI DSS 4.0.1 | Listed. Sierra says it holds Level 1 service provider certification |
| ISO 27001:2022 and ISO 42001:2023 | Listed |
| FedRAMP High | Listed |
| GDPR, CCPA, CSA STAR, EU AI Act | Listed |
Healthcare customers on Sierra's industry page include Sutter Health, Clover Health, and WeightWatchers. No public page reviewed for this article describes Sierra's business associate agreement (BAA) or its terms. If patient data will pass through the agent, get the BAA terms in writing before you sign. The checks to run on any vendor are in HIPAA chatbot vendor questions.
Sierra vs SiteGPT
Sierra and SiteGPT are built for different buyers. Sierra runs agents that act across voice and messaging for companies with six-figure budgets. SiteGPT runs an agent trained on your own content for teams that want a known price and a launch in days.
| Sierra | SiteGPT | |
|---|---|---|
| Buying | Contact form and sales process | Self-serve, 7-day trial (card required) |
| Price | Not published. Outcome-based | $39, $79, or $259 a month billed yearly. $59, $129, or $429 billed monthly |
| Channels | Web, mobile app, SMS, WhatsApp, Apple Business Chat, email, voice, ChatGPT | Website chat, Slack, Messenger, Google Chat, Zendesk, Crisp, Freshdesk, Zoho SalesIQ |
| Actions | Takes actions in connected systems, including multi-day work with Horizon | Captures leads and sends messages, leads, and escalations to webhooks. No refunds or account changes |
| Knowledge | Built from SOPs, transcripts, and documents | 12+ source types, including websites, PDFs, Google Drive, Notion, GitHub, YouTube, and help centers, with auto-sync |
| Human handoff | Contact center handoff and Live Assist for reps | On every plan, with email alerts and agent takeover in chat history |
| HIPAA | Listed, with a 2026 audit report. BAA terms not public | BAA published and available on Enterprise only |
SiteGPT's BAA sits on the Enterprise plan only. A covered workspace also limits what the agent can reach. Patient data stays in end-user conversations, training content must be free of it, and connected apps and chat integrations are off by default. The details are on the SiteGPT HIPAA page.
Both put an AI agent in front of customers. They differ on what the agent can do and on how you buy it.
Choose Sierra when
- Voice calls are a large share of your contact volume
- The agent must complete tasks such as bookings or cancellations
- You want to pay per outcome under a negotiated contract
- You need FedRAMP High or PCI DSS Level 1
Choose SiteGPT when
- Your docs and help center already answer most questions
- You need the monthly price before you start
- You want to test on your own content this week
- Your team handles the cases the agent cannot
Who should buy Sierra
| Scenario | Best pick | Why |
|---|---|---|
| Consumer brand with millions of calls a year | Sierra | Voice in 55+ languages with outbound calling, and Rocket Mortgage runs over 1 million outbound dials a month. |
| Government or public-sector buyer | Sierra | FedRAMP High is listed on its trust center. |
| Healthcare provider with patient data | Sierra or SiteGPT Enterprise, BAA first | Sierra lists HIPAA with an audit report. SiteGPT publishes its BAA. Get terms in writing either way. |
| Mid-size SaaS team under 5,000 conversations a month | SiteGPT or Intercom Fin | Both publish prices and let you test before a sales call. |
| Team that wants to compare two enterprise agents | Sierra and Decagon | Both sell custom contracts, run voice, and share customers such as Chime. |
Fin, Ada, Zendesk, and Gorgias are ranked alongside Sierra in the best AI customer support agents.
FAQ
What is Sierra AI?
Sierra is a conversational AI platform that builds AI agents for customer experience. Its agents answer and resolve conversations across web chat, mobile apps, SMS, WhatsApp, email, and voice.
Sierra was founded by Bret Taylor, former co-CEO of Salesforce, and Clay Bavor, who led Google Labs. Customers include SoFi, Rocket Mortgage, Airtable, and Sutter Health.
How much does Sierra cost?
Sierra does not publish prices, and there is no trial or self-serve sign-up. It uses outcome-based pricing: you pay when the agent completes an agreed outcome, such as a resolved conversation or a saved cancellation.
Conversations transferred to a person are typically not charged. Estimates of about $150,000 a year come from competitors and aggregators, not from Sierra.
Does Sierra have a free trial?
No. As of September 2026 Sierra has no free trial, no free plan, and no sign-up page. New buyers fill in a contact form and Sierra's team reaches out.
Is Sierra AI worth it?
Sierra is worth evaluating for large companies with high volume across voice and messaging that want outcome-based contracts. Published results include 80% resolution at Airtable and a 33-point NPS gain at SoFi. It holds 4.5 out of 5 on G2 from 128 reviews.
It does not suit small teams that need a price up front or want to launch in days.
What is Sierra's G2 rating?
Sierra holds 4.5 out of 5 on G2 from 128 reviews as of 14 September 2026. Ninety reviews are five stars, 36 are four stars, and 2 are three stars. G2's summary names ease of use and efficiency as the most common praise and cost as the most common complaint.
Is Sierra HIPAA compliant?
Sierra's trust center lists HIPAA and offers a 2026 HIPAA audit report on request, alongside SOC 2 Type II, ISO 27001, ISO 42001, PCI DSS 4.0.1, and FedRAMP High. Its healthcare customers include Sutter Health.
No public Sierra page reviewed states the terms of its business associate agreement (BAA), so confirm them during the sales process.
What languages does Sierra support?
Sierra's voice agents speak more than 55 languages and can switch language during a call. Its Ghostwriter launch post states that agents built with Ghostwriter work in over 30 languages across voice, chat, and email.
What is Sierra Ghostwriter?
Ghostwriter, launched on 25 March 2026, is Sierra's agent-building agent. You give it standard operating procedures, support call transcripts, process documents, whiteboard photos, or audio recordings. It produces a production-ready agent across voice, chat, and email.
What is the difference between Sierra and SiteGPT?
Sierra is an enterprise agent platform that takes actions across voice and messaging, sold through a sales process with outcome-based contracts. SiteGPT is a self-serve AI agent trained on your own content, with flat monthly plans from $39 a month billed yearly and a 7-day trial.
SiteGPT answers and hands off to people. It has no voice channel and does not take account actions by itself.
What are the best Sierra alternatives?
Decagon is the closest match, with agents across chat, email, and voice and a similar sales-led model. Intercom Fin publishes a price of $0.99 per resolution. Ada suits enterprises already on Zendesk or Salesforce. SiteGPT suits smaller teams that want a flat price and a launch in days.
Sources
- Sierra: homepage, about, Agent Studio, Agent SDK, channels, voice, trust and reliability, trust center, healthcare
- Sierra blog: outcome-based pricing, Ghostwriter, Horizon, Voice Personas
- Sierra customers: Airtable, Chime, SoFi, Singtel, Rocket Mortgage
- Third parties: TechCrunch funding report, TechCrunch on forward-deployed engineers, Salesforce Ben, Five9 documentation, Quiq estimate, AI Agent Square estimate, G2
- SiteGPT: pricing, human support docs, webhooks docs, HIPAA