Synthflow
by Synthflow AI
No-code platform to build and run AI voice agents for phone calls
Last reviewed 2026-06-18
Synthflow is an end-to-end voice AI platform for building, deploying, and running AI phone agents without code. Teams design agents in a visual Flow Designer or via API, connect their own telephony or use Synthflow's in-house carrier, and deploy agents that field inbound calls and run outbound campaigns end to end: answering questions, qualifying leads, booking appointments against connected calendars, warm-transferring to humans, and triggering custom API actions mid-call. It targets contact centers, agencies (with a white-label and reseller program), and businesses that want production voice agents without building real-time voice infrastructure themselves. Designing and configuring agents is human-driven and supervised; a deployed agent conducts the live phone conversation autonomously.
What it can do
Run live phone calls end to end
AutonomousA deployed agent handles full inbound or outbound phone conversations, answering questions and qualifying callers in real time without a human on the line.
sourceBook appointments against connected calendars
AutonomousChecks availability and schedules appointments in real time on connected calendars (Cal.com, GoHighLevel) during a call.
sourceWarm-transfer and trigger actions mid-call
AutonomousRoutes calls to a human via warm transfer and fires pre-configured custom actions and API calls during the conversation; the endpoints and rules are set up and supervised by the human team.
sourceBuild voice agents in a no-code Flow Designer
SupervisedDesign and configure agents as visual flows or via API, with telephony, voice, and integrations connected by the human builder; design and tuning are human-driven.
source
Strengths
- +Genuinely no-code visual builder with fast setup, a common point of praise in reviews
- +In-house telephony plus broad SIP and CRM integration, with a white-label and reseller program for agencies
- +Natural low-latency voices (ElevenLabs) and a free pay-as-you-go tier to start
Limitations
- −Per-minute cost adds up at volume once LLM and telephony are stacked on the voice-engine rate
- −LLM choice is OpenAI-centric in practice rather than fully model-agnostic
- −Reviewers report latency spikes, barge-in handling issues, and shallow analytics on harder calls
Overview
Synthflow is a no-code platform for building, deploying, and running AI voice agents that handle phone calls in production, for both inbound and outbound use. It is positioned as an end-to-end voice AI platform with in-house telephony.
What it does
Teams design agents in a visual Flow Designer or via API, then deploy them to field inbound calls and run outbound campaigns. A deployed agent runs the full live conversation: answering questions, qualifying leads, booking appointments on connected calendars, warm-transferring to a human, and firing pre-configured custom actions and API calls mid-call. The live call runs autonomously; building and tuning agents is human-driven.
Integrations & setup
In-house native telephony plus bring-your-own carrier over SIP (Twilio, Telnyx, RingCentral, Vonage); CRMs including Salesforce, HubSpot, and GoHighLevel; calendars (Cal.com, GoHighLevel); Zapier; and WhatsApp Business Calling. The platform exposes a REST API, webhooks, and custom actions (function calling). Voices are provided via ElevenLabs; the LLM layer is selectable but OpenAI-centric in practice.
Pricing
Usage-based pay-as-you-go. The voice-engine rate is around $0.09/min, with the LLM (about $0.02-0.05/min) and telephony billed on top, so all-in cost typically runs higher. There is a free PAYG tier, custom enterprise pricing, and a paid White-Label and Reseller Toolkit (reported at $2,000/month).
Traction
Synthflow has raised a reported ~$30M total: a 2024 seed round led by Singular and a $20M Series A led by Accel in June 2025 (reported figures, not audited).
Best for / not for
Best for SMBs, contact centers, and agencies that want production voice agents without building voice infrastructure, and for resellers who want to white-label. Less suited to teams that need a fully model-agnostic LLM choice or the lowest possible per-minute cost at high volume.
Alternatives
Retell AI and Vapi are API-first voice agent platforms; Bland AI runs an owned in-house voice stack.
What people are saying
We aggregate real LinkedIn discussion into sentiment for the agents people search most. Synthflow isn't tracked yet, want it added? Request tracking.
FAQ
Is a Synthflow agent autonomous?+
On a live call, yes: a deployed agent runs the full phone conversation end to end, including booking appointments and triggering pre-configured actions, without a human on the line. Designing and tuning the agent is human-driven and supervised.
How does Synthflow charge?+
Usage-based per minute. The advertised voice-engine rate is around $0.09/min, with the LLM and telephony billed on top, so realistic production cost is higher. There is a free PAYG tier, an enterprise plan, and a paid white-label and reseller toolkit.
Sources
- Synthflow (official site) · accessed 2026-06-18
- Synthflow pricing (official) · accessed 2026-06-18
- Synthflow raises $20M Series A (official) · accessed 2026-06-18
- Synthflow SIP / telephony documentation · accessed 2026-06-18
Last reviewed 2026-06-18