Retell AI vs Vapi
Retell AI vs Vapi: side-by-side comparison of two voice agent platforms systems — architecture, taxonomy, license, pricing, MCP/A2A support, and direct edges.
How they relate
- Retell AI competes with Vapi — Direct competitor to Vapi with proprietary-model focus.
Cost & capability
| Retell AI | Vapi | |
|---|---|---|
| Capability band | competent | competent |
| Capability composite | 53 | 56 |
| Cost tier | mid | mid |
| Use cases | Latency Sensitive, Scoped Agentic | Latency Sensitive, Scoped Agentic |
Where they differ (13)
Rows where both sides have data and the values disagree — the shortlist of dimensions that actually distinguish these two systems.
| Retell AI | Vapi | |
|---|---|---|
| Capability composite | 53 | 56 |
| Type | Developer platform for AI voice agents (low-latency) | Developer platform for AI voice agents (programmable telephony) |
| Created | 2024 (YC S24) | 2023 (YC W23) |
| GitHub | github.com/RetellAI (SDKs only) | github.com/VapiAI (SDKs only) |
| Pricing | Pay-as-you-go $0.07-$0.31/min for voice agents (Retell voice infra $0.055/min plus TTS and LLM components), $10 free credits, 20 concurrent calls included; Enterprise custom | Per-minute usage ($0.05/min base + provider passthrough) |
| Funding | $4.6M seed Aug-2024 (BoxGroup + others) | $20M Series A Dec-2024 (Bessemer); $130M val |
| Backend storage | Call state in Retell-managed DB | Call state in Vapi-managed DB; transcripts retained per config |
| Deployment | Cloud-managed | Cloud-managed; private deployments on Enterprise tier |
| API surface | REST API + Python/JS/Go SDKs; webhooks | REST API; SDKs (Python, JS, React); webhooks |
| Multi-tenancy | Multi-tenant cloud | Multi-tenant cloud; Enterprise dedicated tier |
| MCP | yes — agents can call MCP tools during live calls | yes — Vapi MCP server (remote https://mcp.vapi.ai/mcp, Streamable HTTP; VapiAI/mcp-server, MIT); assistants can also call MCP tools |
| Optimised for | Sub-800ms voice turn latency with vertically-integrated stack | Building phone-call voice agents quickly with composable STT/LLM/TTS |
| Anti-fit | Telephony focus; smaller funding than Vapi; per-minute pricing | Telephony-centric — not for in-app voice UX; per-minute pricing scales fast at high volume |
At a glance
| Retell AI | Vapi | |
|---|---|---|
| Section | Voice agent platforms | Voice agent platforms |
| Tier | T1 | T1 |
| Type | Developer platform for AI voice agents (low-latency) | Developer platform for AI voice agents (programmable telephony) |
| Created | 2024 (YC S24) | 2023 (YC W23) |
| GitHub | github.com/RetellAI (SDKs only) | github.com/VapiAI (SDKs only) |
| Pricing | Pay-as-you-go $0.07-$0.31/min for voice agents (Retell voice infra $0.055/min plus TTS and LLM components), $10 free credits, 20 concurrent calls included; Enterprise custom | Per-minute usage ($0.05/min base + provider passthrough) |
| Funding | $4.6M seed Aug-2024 (BoxGroup + others) | $20M Series A Dec-2024 (Bessemer); $130M val |
| Backend storage | Call state in Retell-managed DB | Call state in Vapi-managed DB; transcripts retained per config |
| Deployment | Cloud-managed | Cloud-managed; private deployments on Enterprise tier |
| API surface | REST API + Python/JS/Go SDKs; webhooks | REST API; SDKs (Python, JS, React); webhooks |
| Multi-tenancy | Multi-tenant cloud | Multi-tenant cloud; Enterprise dedicated tier |
| MCP | yes — agents can call MCP tools during live calls | yes — Vapi MCP server (remote https://mcp.vapi.ai/mcp, Streamable HTTP; VapiAI/mcp-server, MIT); assistants can also call MCP tools |
| A2A | searched not found | searched not found |
| OpenTelemetry | searched not found | searched not found |
| Optimised for | Sub-800ms voice turn latency with vertically-integrated stack | Building phone-call voice agents quickly with composable STT/LLM/TTS |
| Anti-fit | Telephony focus; smaller funding than Vapi; per-minute pricing | Telephony-centric — not for in-app voice UX; per-minute pricing scales fast at high volume |
Pros & cons
Retell AI
Pros: Latency-first positioning; SOC 2 + HIPAA; YC distribution; clean SDKs.
Cons: Smaller than Vapi; per-minute economics at scale; proprietary stack reduces flexibility.
Vapi
Pros: Category-leading mindshare; Bessemer-backed; SOC 2 + HIPAA; mature webhooks + SDKs.
Cons: Per-minute economics at scale; provider-passthrough means triple vendor exposure (STT + LLM + TTS).