Synthflow
Synthflow is an enterprise voice AI platform that builds and runs agents handling inbound and outbound phone calls. It combines a no-code flow builder, in-house telephony and 200+ integrations to automate support, scheduling and lead qualification.
What is Synthflow?
Synthflow is a voice AI platform for automating business phone calls at scale. Published by AgentFlow AI GmbH, founded in Berlin in 2023, it lets a company design, test, launch and monitor AI agents that answer inbound calls and place outbound ones. The company previously traded as Fine-Tuner, a no-code AI agent builder; after the pivot the fine-tuner.ai domain now serves the application dashboard and sign-in screen, while the product site itself is synthflow.ai.
The platform is organised around a four-stage framework the vendor calls BELL: Build, Evaluate, Launch, Learn. Agents are assembled in a visual Flow Designer, with nodes for greetings, conversation steps, branching, call transfer, real-time booking and call termination. A multi-agent system lets subflows act as specialists so complex logic stays readable. Before going live, every agent can be exercised in a Test Center through simulated calls, custom evaluations and an LLM-as-judge check.
What sets the offering apart is that the telephony is owned in house. Synthflow runs its own network rather than reselling a carrier, which it credits for latency under 100 ms on the network and under 800 ms end to end, alongside a claimed 99.99% uptime. Customers can also bring their own SIP trunk or Twilio account, and the platform advertises compatibility with Cisco, Avaya, Genesys, RingCentral and 8x8.
Under the hood the agents combine OpenAI models for reasoning, Deepgram and a native Synthflow engine for speech-to-text, and ElevenLabs for speech synthesis. Thirty-three agent languages are listed in the documentation, plus a multilingual mode that switches automatically between ten of them. Beyond voice, the same platform now drives chat, SMS and WhatsApp agents.
The vendor reports 65 million-plus customer calls, more than 200 integrations, 30-plus countries served and over 100 enterprise teams. Data residency is selectable between an EU cluster, a US cluster and a legacy Global cluster, and a REST API plus an MCP server are available for deeper integration.
What it does
- Answer inbound calls and route each one to the right team or workflow
- Place outbound calls for lead qualification, reminders and follow-ups
- Book, reschedule and confirm appointments straight into connected calendars
- Read and update CRM records live, during the conversation
- Hand the call to a human when sentiment or repeated failures trigger escalation
- Detect voicemail and adapt the outcome of the call accordingly
- Analyse every conversation afterwards and export the call data
When to use Synthflow / When not to
A quick filter to help you decide if Synthflow is the right fit.
When to use Synthflow
- BPO and contact centre operations leaders who need to absorb tier-1 volume and overflow calls without adding headcount
- Customer service and CX teams running always-on inbound support, call routing and after-hours answering
- Sales and revenue teams automating outbound lead qualification, reactivation campaigns and demo scheduling
- Healthcare, dental and clinic administrators handling appointment booking, reminders and patient triage by phone
- Agencies and resellers selling white-labelled voice agents under their own brand, with sub-accounts and rebilling
When not to use Synthflow
- Individuals and consumers, since the terms restrict the service to entrepreneurs within the meaning of Section 14 of the German Civil Code
- Small teams on a tight budget, as the only published tier starts at USD 30,000 per year
- Anyone looking for a voice cloning studio, because cloning has to be done in a separate ElevenLabs account and imported
- Use cases that require the agent itself to give legal, financial or medical advice, which the vendor explicitly rules out
- Buyers who may need to move data residency later, because the cluster picked at workspace creation cannot be changed
How to use Synthflow
A typical end-to-end flow, from setup to results.
- Create a workspace and choose its data cluster, Global, US or EU, keeping in mind that this choice is permanent
- Start an agent from the library of industry templates or build one from scratch
- Set the prompt, voice, language, transcriber and call behaviour in the unified Agent Editor
- Lay out the conversation in the Flow Designer, adding branches, custom actions, call transfer and real-time booking nodes
- Load a knowledge base from a file, a URL or manual entry, then define variables and memory
- Connect the CRM, calendar and contact-centre tools the agent has to act on
- Test the agent manually, then run simulations and custom evaluations in the Test Center
- Attach a phone number, through Synthflow telephony, a SIP trunk or your own Twilio account
- Publish to live, keeping the version history so you can roll back without downtime
- Track analytics, logs and Auto-QA results, then export the call data for deeper analysis
Pros & Cons
Pros
- Owning the telephony network gives real control over routing, latency and call quality, with no carrier lock-in
- The whole agent lifecycle is tooled, from building and testing to launch and continuous monitoring
- The terms rule out training on customer input and output, which is an unusually clear contractual commitment
- Data residency is selectable and a fully EU cluster exists, from a publisher based in Germany
- Broad compliance base: SOC 2, HIPAA, PCI DSS, ISO 27001 and GDPR, with a DPA on request and a published subprocessor list
- An AI Transparency Statement is published under the EU AI Act, which few competitors in this category do
- More than 200 integrations and a full white-label layer for agencies and resellers
Cons
- Only one price is public, and it is a USD 30,000 annual floor, which puts the tool out of reach for small teams
- Detailed pricing is quote-only, scoped on volume, concurrency, telephony, integrations and security needs
- The service is reserved to businesses; the terms exclude consumers outright
- The data region is locked at workspace creation and cannot be changed afterwards
- On the default Global cluster, live call processing may run in the United States even though storage stays in the EU
- WhatsApp and SMS chat agents are limited to US workspaces, and no support email address is published
- Voice cloning is not performed on the platform and requires a separate ElevenLabs account
Pricing & Plans
There is no permanent free plan advertised on the pricing page. Enterprise contracts start at USD 30,000 per year, with the final figure scoped around call volume, concurrency, telephony setup, integrations, security requirements and launch support. Separately, the vendor's own FAQ states that building an agent costs nothing upfront and that billing switches to a pay-as-you-go model once the agent goes live, although no rate is published for that route.
- annual contracts from USD 30
- 000
- covering a contractually scoped SLA and support terms
- Synthflow native telephony
- SIP trunking or approved enterprise telephony
- custom concurrency
- routing
- escalation and fallback planning
- designing call flows
- voicemail detection and integrations at no upfront cost
- before any agent goes live
- usage-based billing on the calls and chats actually conducted once an agent is launched
- with no published rate
- sub-accounts
- permissions
- custom pricing and rebilling for agencies
- priced on request
Data, GDPR & hosting
A consolidated view of how Synthflow handles your data.
GDPR overview
GDPR implementation is concrete and documented. The controller is established in Berlin, so the GDPR and the German Federal Data Protection Act apply directly. The privacy policy states each purpose with its Article 6 legal basis, lists data subject rights under Articles 15 to 21 and covers withdrawal of consent under Article 7. A Data Protection Officer is designated and reachable at privacy@synthflow.ai. Transfers outside the EU rely on the European Commission standard contractual clauses under Article 46(2)(c). Sensitive personal data is stored exclusively on EU servers certified to DIN ISO/IEC 27001. A Data Processing Agreement is provided on request, a subprocessor list is published, and an AI Transparency Statement is issued under Articles 50 to 54 of the EU AI Act, version 1.1 effective 29 July 2026.
Who owns the data?
AgentFlow AI GmbH, based in Berlin, operates the platform. For the personal data flowing through customer agents it acts as processor while the customer stays controller of its own callers' data. That processing is governed by a Data Processing Agreement which Synthflow makes available on request and which is then executed between the parties under Article 28 GDPR. The categories handled are call recordings and transcripts, identifiers such as phone numbers and caller ID, usage data, and optional CRM records. A Data Protection Officer, Hakob Astabatsyan, is designated, and data subject requests are directed to privacy@synthflow.ai.
Reuse rights
Subscribers keep the rights to their own inputs and outputs. Synthflow commits contractually not to use customer input or output to train, fine-tune or otherwise improve its own models or those of any third party, and states it processes that material solely to deliver the software, including passing it to the third-party applications the customer has connected. No automated individual decision-making or profiling within the meaning of Article 22 GDPR is performed. Because no training takes place at all, no opt-out switch is offered and none is needed. Declared subprocessors are Google Cloud Platform for hosting, OpenAI, Deepgram, ElevenLabs, Bubble.io and Twilio.
Data retention & training
Hosting summary
Hosting is organised into three clusters chosen when a workspace is created. The EU cluster keeps both storage and compute in the European Union, the US cluster keeps both in the United States, and the legacy Global cluster stores data in the EU while live call processing may run in either region depending on traffic and routing. This choice is permanent and cannot be changed afterwards. Google Cloud Platform is the declared hosting subprocessor. The privacy policy adds that sensitive personal data is stored exclusively on EU servers certified to DIN ISO/IEC 27001, and the AI Transparency Statement says all data is hosted within the EU or under adequate safeguards. Transfers to third countries rely on the European Commission standard contractual clauses. One caveat: if a customer brings its own Twilio account into an EU workspace, some Twilio API requests run in Ireland and others fall back to the United States. The public IP of the domain resolves to a Cloudflare anycast node, which says nothing about where data actually lives.
Things to keep in mind
Risks and trade-offs to weigh before adopting Synthflow.
- Callers may not realise they are talking to a machine: disclosing that the agent is artificial is left to the customer, not enforced by the platform
- Outbound campaigns carry real legal exposure, since the vendor places consent collection and telecom compliance entirely on the customer
- The vendor acknowledges its agents can hallucinate, misread tone or misroute a call, particularly with non-standard speech or noisy lines
- Call recordings and transcripts are sensitive personal data, and the default 90-day retention can only be changed by contract
- Choosing the Global cluster by default can send live call processing to the United States even when storage stays in the EU
- Automating tier-1 calls can erode the informal knowledge front-line staff build up, and quietly reduce the human contact some callers need
- Trusting the agent's summaries without sampling real recordings can hide failures that only a human listening to the call would catch
Setup & Integrations
Technical difficulty
Building an agent requires no code: the Flow Designer is visual and industry templates are supplied ready to use. Real complexity sits in telephony, where numbers, SIP trunks and integration with an existing PBX or contact-centre stack need proper planning, and in the permanent choice of data cluster made at the very start. Enterprise contracts include forward-deployed engineers, onboarding, testing, training and launch support, and the vendor advertises deployment in about three weeks with measurable return within 60 days. A REST API and an MCP server cover more advanced cases.
Deployment
Integrations
Supported languages
Behind Synthflow
Fundraising
Social
Resources
All the official URLs gathered for verification and reference.
Alternatives
Tools that compete with or complement Synthflow.
Frequently asked questions
What is Synthflow?
Why does the fine-tuner.ai address lead to Synthflow?
How much does Synthflow cost?
Is there a free trial?
Is my data used to train AI models?
Where is the data hosted?
How long is data kept?
Which languages do the agents speak?
Can I connect my own telephony and tools?
Can individuals sign up?
Should you pick Synthflow?
Synthflow is a mature product with a clear position: it targets enterprise phone operations, not self-service experimentation. Its main differentiator is genuine, and unusual in this category, since it runs its own telephony network instead of reselling a carrier, and pairs that with tooling for the whole agent lifecycle rather than a builder alone. Testing, versioning, rollback, real-time monitoring and post-call analysis are all part of the platform rather than add-ons.
For a European buyer the compliance base is a real argument. The publisher is a Berlin company subject to the GDPR, a fully EU cluster is available, the terms rule out training on customer data, a DPA is provided on request, the subprocessor list is published, and an AI Transparency Statement is issued under the EU AI Act. That combination is more explicit than most competitors offer.
The obvious brake is commercial. A single published tier at USD 30,000 per year, with everything else on quote, excludes small and mid-sized teams and makes cost comparison hard. The free building path mentioned in the FAQ and the enterprise floor on the pricing page tell two different stories that the site does not reconcile. Two structural constraints also deserve attention before signing: the data cluster cannot be changed after the workspace is created, and on the default Global cluster live processing may leave the EU even though storage does not.
One practical point: the fine-tuner.ai address that still circulates is the former brand and now serves only the application, so check which page you land on. Worth evaluating for organisations with high call volumes and an existing telephony stack; considerably less relevant for a small business or an individual.
- Choosing a selection results in a full page refresh.
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