Sierra vs Vapi
A side-by-side comparison of Sierra and Vapi on what each one charges, what it meters, and which plan every capability actually sits on.
The short answer
2 of the 10 capabilities tracked on both differ.
| Measure | Sierra | Vapi |
|---|---|---|
| Starts at | Sales-gated | Sales-gated |
| AI billed at | Not published | $0.01 per AI interaction |
| Included, where the other says no | 0 capabilities | 0 capabilities |
Capability by capability
2 of the 10 capabilities tracked on both products differ.
Channels
| Capability | Sierra | Vapi |
|---|---|---|
| IncludedNo plans are published, so plan gating cannot be assessed. | Not published | |
| Live chat | IncludedNo plans are published, so plan gating cannot be assessed. | IncludedBuild, at $0.005 a message. A Chat API with streaming and non-streaming modes, an OpenAI-compatible endpoint, session management, and a drop-in web widget that runs in chat or voice mode from one script tag. |
| Voice | IncludedNo plans are published, so plan gating cannot be assessed. | IncludedBuild. Voice is the product, billed at $0.05 a minute of connected call time on top of provider cost. |
| SMS | Not published | IncludedBuild, billed on the same $0.005 a message meter as chat. Requires a 10DLC-approved Twilio number, and inbound SMS is documented as US only. |
| IncludedNo plans are published, so plan gating cannot be assessed. | Not published |
AI resolution
| Capability | Sierra | Vapi |
|---|---|---|
| Autonomous resolution agent | IncludedThe whole product. Sierra bills only on outcomes such as "a resolved support conversation", which presupposes autonomous resolution. | Not published |
| Resolution over knowledge base | Not published | IncludedA query tool retrieves from knowledge bases built in Vapi, billed as a knowledge-base line in the call cost array. A custom knowledge base server is the documented alternative, and keeps the corpus out of Vapi entirely. |
| Action-taking (API calls) | Included"Enable your agent to take action to assist customers by securely connecting it with any internal or external system", including systems of record from order management to CRM. | IncludedTools are first-class and versioned: an API Request tool with configurable retries, custom function tools, client-side tools in the web SDK, argument encryption, and a tool rejection plan. Squad handoffs carry a contextEngineeringPlan controlling how much conversation and how many tool results move to the next assistant. |
| Handoff to human | IncludedEscalation exists and is usually not billed: "if a case needs to be escalated, in most cases, there's no charge". The exceptions are unpublished. | IncludedBlind transfer, warm transfer, assistant-based warm transfer, dynamic destinations and on-hold specialist transfer are each documented separately. Nothing published says the $0.05 hosting meter stops when a call reaches a human. |
| Guardrails & citations | IncludedGuardrails are published as "supervisory layers to reduce hallucinations, ensure security, and prevent abuse", and PII is "automatically encrypted and masked". Citation behaviour is not addressed anywhere, so half of this attribute is Unknown. | Not published |
| Multilingual AI | IncludedSierra publishes "voice, chat, email, and WhatsApp in 59 languages", available 24/7/365. | Via middlewareDelivered by whichever third-party transcriber you select rather than by Vapi, which ships no speech recognition of its own and publishes no language count. The docs compare providers instead: Deepgram 100+ languages with auto-detection, Google STT 125+, Gladia 110+, AssemblyAI 18, while Azure, Whisper, Speechmatics and Talkscriber carry many languages but cannot detect them. So whether an agent can switch language mid-call is a consequence of a configuration choice, and the documented way to tell the agent it is multilingual is to list the languages in your own system prompt. |
AI voice
| Capability | Sierra | Vapi |
|---|---|---|
| Voice agent | IncludedVoice is listed as a first-class agent channel alongside chat, email and WhatsApp. No per-minute rate or telephony passthrough is published. | IncludedTransport is modular: SIP, WebSocket, WebRTC via LiveKit or Daily, or PSTN through an imported Twilio, Telnyx, Plivo, Vonage, DIDWW, Zadarma, didlogic or Amazon Chime number. Up to five free Vapi US numbers per account, US area codes only. |
| Real-time transcription | Not published | IncludedStreaming recognition from a choice of eleven transcriber providers, or your own over a WebSocket. Both the caller and the assistant are transcribed, which is why a minute of call is two channels of audio on the provider bill. |
| Call summarization | Not published | IncludedCall analysis produces a summary and schema-defined structured outputs after the call, attached to the call record and readable through the API. Under HIPAA mode structured outputs are not stored unless each one is explicitly opted in. |
QA & workforce
| Capability | Sierra | Vapi |
|---|---|---|
| Automated QA coverage | Not published | IncludedScorecards grade every call automatically by awarding points when structured outputs meet conditions you define, landing in call.artifact.scorecards within seconds of call end. No per-call charge is published for grading, unlike Retell's $0.10 a minute. API only for now, by the vendor's own admission. Evals and AI-driven simulations sit alongside for pre-production testing. |
Reporting
| Capability | Sierra | Vapi |
|---|---|---|
| Raw data export | Not published | API onlyEverything comes out through the API or a mirrored bucket; there is no export UI. Recordings and logs are served as 302 redirects to short-lived signed URLs against a private bucket, so a cached URL stops working. |
Enterprise
| Capability | Sierra | Vapi |
|---|---|---|
| SAML SSO | Not publishedNot addressed on the trust and reliability page or any product page. | IncludedEnterprise only, marked "-" against Build on the pricing page. SAML 2.0 or OIDC against any IdP, with Google Workspace, Microsoft Entra ID and Okta named. |
| SCIM provisioning | Not published | NoStated outright in the SSO documentation: "Vapi does not support SCIM provisioning." Members sign themselves up and an administrator invites them, so removing a leaver is a manual step even on an SSO contract. |
| Role-based access control | Not published | IncludedThe pricing page prints RBAC as a Scale row with "-" against Build, while the SSO documentation describes the three roles as ordinary organization behaviour. Which of the two governs a Build account is not resolved by anything published. |
| HIPAA / BAA | IncludedNot assessable; no plans are published. | Paid add-on$2000/mo add-on, priced identically on Build and Scale, or included by negotiation on an Enterprise subscription. A signed BAA is required first, started by emailing security@vapi.ai. Organization-wide with no per-assistant exception, not settable through the API, and mutually exclusive with Zero Data Retention. |
| SOC 2 | IncludedNot assessable; no plans are published. | IncludedThe trust center lists SOC 2 with reports behind an access request, while the pricing page prints SOC2 as a Scale-only row. The certification is account-wide; the report and the contractual commitment are what the enterprise tier buys. |
| ISO 27001 | IncludedNot assessable; no plans are published. | Not publishedAbsent from the trust center compliance list, which enumerates CCPA, GDPR, SOC 2 and PCI DSS v4.0.1, and claimed nowhere in the docs. |
| GDPR | IncludedNot assessable; no plans are published. | IncludedListed on the trust center alongside CCPA. The compliance page names its legal bases, enumerates data subject rights including portability, publishes its third-party processors, and covers transfers to the United States under standard contractual clauses. A full subprocessor register is public, with each entry showing purpose and processing location, which is more than most of this census publishes. |
| Data residency | Not publishedNo region list appears on the trust and reliability page or anywhere else on sierra.ai. PCI cardholder data runs on "dedicated PCI certified infrastructure" segregated from the core platform, which is infrastructure segregation rather than a residency or VPC option. | IncludedAn isolated EU region exists (dashboard.eu.vapi.ai, api.eu.vapi.ai, sip.eu.vapi.ai) with its own outbound IP block, and an organization belongs to exactly one region. It is closed to new self-serve signups: EU support and self-serve growth are frozen until 2027, feature parity with the US is not guaranteed, and EU residency is reachable only through sales. |
| Data retention policy | Not publishedNo retention window is published. One third-party directory says "configurable per DPA"; unverified and not merged. | IncludedFixed rather than configurable on Build: 14 days of call history, 30 days of chat history. Custom on Scale. Per-assistant artifactPlan flags switch recording, logging and transcription off individually, and PCI mode deletes recordings and transcripts permanently when no bucket or webhook is configured. |
| Right-to-erasure tooling | Not published | IncludedBy request to support@vapi.ai under GDPR and CCPA. The privacy policy states that retention depends on the customer's configuration and that data is deleted on request, while also reserving the right to retain recordings, transcripts and logs to train and improve the AI models. |
Developer
| Capability | Sierra | Vapi |
|---|---|---|
| REST API | Not publishedNo public API reference is published on sierra.ai. The Agent SDK page describes extensibility without documenting an API. | IncludedNo plan gate. A private key from the dashboard works on Build. |
| Webhooks | Not published | IncludedServer URLs with authenticated server events, an end-of-call-report event, campaign pre-dial webhooks, and local development tooling in the CLI. |
| SDKs | IncludedThe Agent SDK is a published product surface, described as extensible so customers can write and connect their own integrations. No public API reference is published. | IncludedServer SDKs for TypeScript and Python, real-time SDKs for web, iOS, Flutter, React Native and a vanilla script tag, an official CLI, and a docs MCP server. Custom transcriber, custom LLM and custom TTS servers are each documented, so every pipeline stage except the proprietary orchestration layer can run on your own infrastructure. |
Both entries last checked Sep 9, 2026.
What Sierra costs
- Billing unit
Per outcome - Free tier
Not published - AI pricing
Not published - Vendor calls it
Outcome - Human handoff
Not published - Reopened chat
Not published - AI billing window
Not published - Data export
Not published - Automation export
Not published
7 of 9 not published by Sierra, checked
What Vapi costs
- Billing unit
Pure consumption against a prepaid credit balance - Free tier
No - AI pricing
$0.05 per minute - Vendor calls it
Vapi Hosting - Human handoff
Still billed - Reopened chat
Not published - AI billing window
Not published - Data export
Self-serve - Automation export
Full
2 of 9 not published by Vapi, checked