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Natural conversations, mid-call actions, built-in telephony, analytics, and a visual agent builder.

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Voice & AI Models Call Experience Knowledge & Intelligence Channels & Reach Agent Builder Platform

4.1

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10,000+ teams

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Voice & AI Models

Full-duplex audio, 32+ languages, and your choice of AI model — configured from the dashboard.

Full-duplex audio

Both sides talk simultaneously with graceful interruption handling.

Real-time turn-taking with configurable interruption sensitivity
Minimum word threshold before allowing caller interruptions
Turn detection with 23-language support and ~12ms inference

Natural personality

Listening cues like "uh-huh" and subtle office ambience for realism.

Configurable acknowledgment word list and frequency
Pre-synthesized cues at session start for zero latency
Background audio (e.g., call-center ambience) with adjustable volume

Dozens of voices

OpenAI, ElevenLabs, and AWS Polly with accent, gender, and speed options.

OpenAI TTS: gpt-4o-mini-tts with 10 voices (alloy, ash, ballad, coral, echo, fable, nova, onyx, sage, shimmer)
ElevenLabs: v3 and Flash 2.5 with dynamically fetched premade and professional voices
AWS Polly: generative and neural engines (Danielle, Matthew, Ruth, etc.)

32+ languages

Multilingual voice support across all providers out of the box.

Configurable language per agent for STT, TTS, and LLM independently
Polyglot voices on Nova Sonic support 7 languages simultaneously
Voice best practices injection optional per language

Traditional pipeline

GPT-4.1 / GPT-5 + Deepgram STT + TTS for maximum flexibility.

LLM: GPT-4.1, GPT-4.1-mini, GPT-4.1-nano, GPT-4o, GPT-4o-mini, GPT-5, GPT-5-mini, GPT-5-nano, GPT-5.1, GPT-5.2
STT: Deepgram Nova-3 with configurable language
TTS: OpenAI, ElevenLabs, or AWS Polly — mix and match providers

Speech-to-speech

Nova Sonic 2.0, OpenAI Realtime, Gemini Live, Grok — ultra-low latency.

AWS Nova Sonic 2.0: 16 voices, 7 languages, configurable endpointing (LOW/MEDIUM/HIGH)
OpenAI Realtime: gpt-realtime and gpt-4o-realtime-preview, semantic VAD with eagerness levels
Google Gemini Live: 30 voices (Puck, Charon, Kore, Fenrir, etc.), 59+ languages
Grok Voice Agent: 5 voices (Ara, Rex, Sal, Eve, Leo), 40+ languages, server-side VAD

Per-agent tuning

Temperature, turn detection, and silence thresholds per agent.

Temperature from 0 to 2 (default 1.0) for creativity vs. determinism
Smart turn detection with configurable activation threshold and silence duration
Dynamic system prompts with template variables resolved at call start

Call Experience

Every call aspect is configurable — greetings, noise suppression, mid-call actions, and transfers.

Configurable greetings

AI-generated, pre-defined message, or silent mode.

Dynamic: AI generates greeting from system prompt context
Static: pre-defined message (e.g., "Hi, I am Kelly...")
Silent: agent waits for the caller to speak first

Noise suppression

Deep-learning noise cancellation for clearer conversations.

DTLN deep-learning noise cancellation plugin
Configurable strength from 0 (off) to 1 (maximum)
Applied to caller audio for clearer agent comprehension

Cost & spam controls

Max duration, silence hangup, and inactivity reminders.

Inactivity reminders with configurable interval (e.g., 10-15s) and max count
Max call duration up to 1 hour (3,600,000ms)
End call after configurable silence timeout (180s-600s)
Configurable ring duration before timeout (default 30s)

Look up information

Query any system for order status or account details mid-call.

Custom HTTP tools with configurable method, headers, body, and timeout
Response variables capture values via JSONPath extraction
Values injected into conversation context for follow-up use

Book appointments

Real-time availability via Calendly and Cal.com.

Calendly integration with event type URI and timezone configuration
Cal.com integration with full availability checking
Real-time slot availability and instant booking confirmation

Call any API

HTTP endpoints with configurable auth and request templates.

Configurable HTTP method, headers, auth, body templates, and query params
Body templates with {{variable}} placeholders resolved at call time
Supports JSON and SOAP/XML response parsing
Strict JSON schema compliance mode for function calls

Transfer calls

Zero-gap audio handoff to humans or external numbers.

Cold transfer via SIP REFER for zero-audio-gap handoff
Transfer to human agents or external phone numbers
Transfer destination automatically logged in call record

Agent-to-agent transfer

Hand off a live call to a different AI agent with a completely new persona.

New agent fully takes over — different voice, LLM, prompt, tools, and knowledge base
Caller stays on the same line with no interruption
Configurable context passing: full conversation history, AI-generated summary, or fresh start
Multiple transfer targets per agent — route to billing, support, or sales based on conversation

Voicemail detection

Detect machines and leave messages or generate AI responses.

Automatic answering machine detection (CPA/AMD)
Three actions: hang up, send static message, or LLM-generated message
Audio resampled 48kHz to 8kHz with G.711 ULAW encoding
Available on outbound calls only

Knowledge & Intelligence

Knowledge base, call analytics, and automatic post-call analysis.

Multiple sources

Crawl web pages, upload PDFs / Word docs, or paste text.

URL crawling with auto-discovery of linked pages, include/exclude path patterns
PDF and Word document upload with size tracking
Direct text input with custom titles

Auto-refresh

Scheduled re-crawling keeps web content current.

Configurable re-crawl interval per URL source
Automatic status tracking: pending, processing, completed, failed
Error messages and progress details per source

Vector search

Semantic retrieval with automatic chunking and deduplication.

OpenAI text-embedding-3-small (1536d) or AWS Bedrock (256d)
Automatic content chunking with token counting and metadata
Content hashing for deduplication across sources
Full-text keyword search fallback alongside semantic search

Analytics dashboard

Volume trends, performance, daily costs, disconnection analysis.

Call volume trends (line chart), calls by agent (bar chart)
Sentiment and outcome distribution (pie/bar charts)
Cost per day with consolidated cost/duration metrics
Disconnection reason analysis and agent performance comparison

Full call detail

Transcript, audio, cost breakdown, latency, and event timeline.

Transcript with speaker labels and tool call visibility
Audio playback synced to transcript — click to seek, auto-highlight during playback
Cost breakdown: LLM input/output tokens, TTS characters, STT minutes
Latency metrics: LLM TTFT, TTS TTFB, end-to-end delay
Events timeline, raw logs, dynamic variables, KB retrieval URLs

Post-call analysis

Automatic summary, sentiment, success evaluation, and outcome.

Call summary (1-3 sentences) and success evaluation (boolean)
Sentiment: Positive / Negative / Neutral / Unknown
Outcome: Contained / Partially Contained / Business Rule Transfer / Early Abandon / Hangup / Agent Escalation / Confusion Transfer / Timeout
Configurable analysis model and custom analysis prompts

Custom extraction

Define additional data points to extract per agent.

Per-agent fields with types: string, boolean, enum, number
Extracted automatically from transcript after each call
Results available via API, dashboard, and webhooks

Webhooks

call_started, call_ended, call_analyzed events with auto retry.

Configurable URL with timeout per webhook
Automatic retry logic with delivery tracking
Response logging for debugging integrations

Channels & Reach

Web widget, phone numbers, SIP trunking, and outbound calling API.

Web widget

Voice or chat on any website — floating bubble or inline embed.

Modes: voice-only, chat-only, or voice + chat simultaneously
Display: bubble (floating button + panel) or inline (embedded in page)
Real-time audio streaming via WebRTC

Fully customizable

Colors, themes, icons, branding, and per-page overrides. White-label ready.

Theme: light / dark / auto with accent color (hex)
Position, visualizer type (aura/wave), layout (side-by-side/stacked)
Custom bubble icon and label, panel width and height
Control visibility: microphone, chat, and leave button toggles
White-label: toggle Blowfish branding off per embed
Security: allowed origins (CORS), rate limiting, Cloudflare Turnstile bot protection

Number marketplace

Search, purchase, and manage phone numbers from the dashboard.

Twilio integration for search, purchase, and management
Filter by region/country with E.164 validation
Assign numbers to agents with inbound/outbound direction tracking

SIP trunking

Inbound/outbound trunks with IP or credential authentication.

Inbound: IP-based (allowed addresses) or credential-based (username/password) auth
Outbound: configurable SIP server, transport (UDP/TCP/TLS/WS/WSS), phone number pool
Custom headers and metadata per trunk

Dispatch rules

Route incoming calls to agents by trunk and phone number.

Route by trunk, inbound number, and metadata
Rule types: individual routing (to agent) or direct routing (to trunk)
Auto-cleanup: outbound trunk deleted when last number removed

Outbound API

Launch calls with per-call prompt, greeting, and metadata overrides.

E.164 format for from_number and to_number
Per-call agent override, greeting, prompt, goodbye, voicemail behavior
Metadata and dynamic variables injected at call start
Form-based key/value builder alongside raw JSON mode

Agent Builder

Build, test, and publish agents entirely from the dashboard.

Visual configuration

Voice, model, prompt, tools, knowledge, and telephony in one place.

Voice catalog organized by provider, gender, accent, age with language filtering
LLM catalog by provider, type (traditional vs. S2S), and billing model
STT catalog with language support metadata

Draft & publish

Edit freely without affecting live agents, publish with one click.

Draft/published state machine for safe editing
Published configs synced to production cache for instant reads
Cron job keeps configs in sync across environments

Dynamic prompts

Template variables like {{caller_name}} resolved at call start.

Variables: {{caller_name}}, {{current_time_{{timezone}}}}, {{user_number}}, {{franchise_id}}
Resolved at call start from metadata and system context
Can reference values captured from previous tool calls

Browser testing

Push-to-talk or open-mic with support for test variables.

Push-to-talk button alongside open-mic mode
Pass custom variables to simulate real call metadata
Full transcript and tool call visibility during test

Voice preview

Listen to voice samples before choosing.

Cached voice samples with signed URLs for instant playback
Listen directly in the voice selector
Organized by provider, gender, accent, and age

Retell migration

Import wizard maps existing Retell agents, prompts, and voices.

Automatic mapping of agents, prompts, tools, voices, and dynamic variables
Provider and voice matching across platforms
One-click migration from Retell AI

Platform

Teams, security, admin tools, and a full developer platform.

Org-based isolation

Each org sees only its own agents, calls, numbers, and data.

Organization-scoped agents, calls, numbers, and knowledge bases
Self-service org creation from the dashboard with org switching
Cross-tab logout synchronization across browser sessions

Auth & roles

Email/password, magic link, Google SSO, admin/member RBAC.

Email/password, magic link (passwordless), and Google SSO
Email verification and password reset flows
Admin and member roles with settings restrictions
Signup approval workflow: pending, approved, or rejected

Super admin

Manage all orgs, user impersonation with audit trail.

Dashboard to manage all organizations and users across the platform
User impersonation with required reason, session expiration, and revocation
Audit log: auth events, admin actions, user activity with IP and user agent

REST API & docs

Full API with interactive OpenAPI reference.

CRUD endpoints for agents, calls, numbers, KBs, telephony, webhooks, voices, LLMs, embeds
Auto-generated OpenAPI reference with interactive API explorer
Internal API for secure agent-to-dashboard communication

MCP server

AI assistants can manage agents, calls, and numbers.

List agents, get call details, list phone numbers, make outbound calls
OAuth 2.1 provider: AI assistants authenticate via standard OAuth flow
Connect to third-party MCP servers with per-server auth and timeout

Webhooks & cron

Call event subscriptions with retry and automated background jobs.

Events: call_started, call_ended, call_analyzed
Configurable URL, timeout, delivery tracking, automatic retry
Automated background jobs: stale call cleanup, KB refresh, config sync

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