OpenPhn vs Vapi.
Voice platform for real-time agents.
Vapi is excellent if you're building real-time voice UX — inbound IVR, live assistants, barge-in heavy conversations. Their SDK surface is voice-first.
Stay on Vapi when…
- ◆Your product is the voice experience itself (e.g., AI receptionist).
- ◆You need deep control over turn-taking, interruptions, and real-time function calls.
- ◆You're optimizing for latency under 300ms on long multi-turn conversations.
Switch to OpenPhn when…
- ◆Your product is NOT a voice app — it's an agent that occasionally needs a phone call. You want outcome JSON, not a voice pipeline.
- ◆You want to declare the shape of the return value and get it back typed, not reconstruct it from a transcript.
- ◆Your stack is already agent-native (OpenClaw, Hermes, LangGraph, CrewAI, MCP) and you want a drop-in skill, not an SDK to wire.
Line by line.
| CAPABILITY | OPENPHN | VAPI |
|---|---|---|
| CORE | ||
| Schema-first outcomes (you declare the JSON shape) | ● | ○ |
| Webhook-native with HMAC signatures + retries | ● | ● |
| First-class MCP server | ● | ○ |
| First-class OpenClaw / Hermes / n8n skills | ● | ○ |
| STACK | ||
| Bring-your-own telephony (Twilio / Vonage / Telnyx) | ● | ● |
| Python + TypeScript SDKs | ● | ● |
| Streaming transcripts on the wire | ● | ● |
| COMPLIANCE | ||
| TCPA call-hour enforcement (server-side) | ● | ◐ |
| Suppression list scrubbing | ● | ◐ |
| SOC 2 Type II | In progress | ◐ |
| PRICING | ||
| Voice + extraction priced separately | ● | ● |
| No markup on carrier minutes | ● | ● |
● full support · ◐ partial or with caveats · ○ not supported
Moving from Vapi.
- 01
Distill your Vapi assistant into an objective
One sentence: what should this call accomplish? Move prompt body into the `context` field for the rare case you need flavor.
- 02
Replace the function-call list with an outcome_schema
Vapi's function-call pattern maps cleanly: each function becomes a field, with its arguments as the field shape.
- 03
Swap the dispatch call
`POST /v1/calls` with your objective, outcome_schema, and consent_type. Remove any assistant-orchestration code — the agent is OpenPhn.
Vapi bills voice + LLM + tools separately; total cost is comparable to OpenPhn Pro for short calls ($0.06–$0.10/min range) but OpenPhn caps extraction at $0.02/min regardless of turns.
See the full OpenPhn pricing →