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vapi.health

Resources

Short guides, curated links, a glossary and FAQ for Vapi voice agents and the voice AI ecosystem.

Short guides

What is Vapi?

Vapi is a developer platform for building real-time voice AI agents. It orchestrates a streaming pipeline of speech-to-text, an LLM, and text-to-speech across telephony providers like Twilio and Vonage.

Vapi vs Retell vs Bland

All three are developer-first voice agent platforms. Vapi bets on provider flexibility, Retell on natural cadence out of the box, and Bland on enterprise outbound throughput.

How voice-agent pricing works

Vapi's $0.05/min covers orchestration. On top of that you pay STT, LLM, TTS, and telephony pass-through — usually another $0.10–$0.20/min in real workloads.

Reading a status page

A green dot means an endpoint is reachable. It does not guarantee upstream providers (Deepgram, OpenAI, ElevenLabs) are healthy — those failures show up as dropped calls or silent turns.

Why CORS limits browser checks

Most voice AI platforms don't return permissive CORS headers, so browser checks confirm DNS/TCP/TLS handshake only. That's why we report reachability, not full call-path health.

Glossary

STT
Speech-to-text; the transcriber that turns caller audio into text (Deepgram, Whisper).
LLM
Large Language Model; decides what the agent says next (GPT-4o, Claude, Gemini).
TTS
Text-to-speech; turns the LLM's response into audio (ElevenLabs, Aura, PlayHT).
First-word latency
Time from caller ending a sentence to hearing the first word of the reply.
Endpointing
How the STT decides the caller has finished a turn (silence + energy threshold).
VAD
Voice Activity Detection; the low-level signal driving endpointing.
Barge-in
Letting the caller interrupt the agent mid-sentence.
Assistant
The bundle of prompt, voice, model, and tools that defines an agent in Vapi.
Tool / function call
A structured JSON handoff from the LLM to your API mid-call.
Concurrency
Number of simultaneous calls your plan can run.
BYOC
Bring Your Own Carrier — plug your own telephony provider via SIP.
BYO provider
Bring your own OpenAI / ElevenLabs / Deepgram keys instead of managed pricing.
Warmup
Pre-loading a TTS voice or LLM route to avoid cold-start on first turn.
Streaming TTS
Audio starts as soon as the first token arrives instead of waiting for the full response.
Turbo / Flash
Low-latency TTS model variants tuned for real-time conversation.

FAQ

What are the best resources for learning Vapi?
Start with the pipeline architecture guide to understand how STT, LLM, and TTS fit together, then read the per-minute pricing breakdown and the latency checklist before shipping a production voice agent.
Where can I check whether Vapi is down?
The vapi.health homepage runs live browser-side reachability checks against the Vapi API and dashboard and embeds the official Vapi status page, with sister pages for Retell AI, Bland AI, and ElevenLabs.
Is Vapi legal in the US?
Yes — Vapi is a developer platform. Voice agent usage rules depend on the jurisdiction and how you use them (recording consent, TCPA, GDPR).
How much does a Vapi call actually cost?
Roughly $0.30–$1.20 for a 3-minute call depending on which STT/LLM/TTS providers you use. See our Vapi pricing per minute guide.
What's the difference between Vapi and Retell?
Vapi gives you fine-grained provider control; Retell ships with tuned natural voices out of the box. Both are strong picks.
Why does this site show reachable but my calls are failing?
Browser checks only see whether public endpoints respond. Failures often come from upstream provider degradation (Deepgram, OpenAI, ElevenLabs) or telephony issues we can't probe from a browser.
Do you place calls or store audio?
No. vapi.health is read-only — we run public reachability checks and link out to each platform.
Where can I find documentation and guides for Vapi?
Vapi.health hosts in-depth technical guides covering latency tuning, cost breakdowns, architecture workflows, and side-by-side platform comparisons between Vapi, Retell AI, and Bland AI.
How do I check if Vapi or voice AI APIs are down?
Use the vapi.health status dashboards to verify live reachability for Vapi, Retell AI, ElevenLabs, and Bland AI APIs, combining browser probes with official vendor status streams.
What tools help calculate Vapi per-minute calling costs?
The vapi.health pricing guides provide full mathematical breakdowns calculating Vapi's $0.05/minute base orchestration fee alongside telephony, STT, LLM token, and TTS audio synthesis costs.