Synthflow AI Review: Hands-On Testing and Insights

The future we dreamed about a decade ago is finally here, and tools like Synthflow AI are changing the game. This software promises “effortless, human-like AI phone calls,” and aims to transform how businesses manage customer interactions.

But is it truly as sophisticated as it sounds? Powered by ChatGPT, Synthflow AI boasts impressive strengths - but it also has its quirks. Setting up an AI assistant feels straightforward, but getting it to work flawlessly can be a different story.

In this Syntflow AI review, I’ll take you through my hands-on experience. You’ll learn how I built my own AI assistant, step by step, and discover the highs and lows of the process. By the end, you’ll have all the information you need to decide if Synthflow’s AI is the right fit for you.

Let’s dive in.

What Is Synthflow AI?

Synthflow AI is a platform that streamlines the creation and management of AI voice assistants to handle live customer conversations. It offers friendly and efficient service anytime by making calls, understanding, and responding naturally like a human would.

Its no-code setup means anyone can create an assistant, and its quick deployment makes integration with your existing systems simple.

Synthflow AI markets itself as your always-available, tireless, and highly capable team of virtual phone assitants with a few key benefits:

• 24/7 Availability: Answer support calls 24/7 or reach out to leads from far-away time zones.
• Improved Customer Experience: With features like real-time booking and quick transfers to real humans, Synthflow AI resolves some of the annoying features people associate with AI chatbots.
• Boosted Sales Conversions: Sales opportunities are addressed immediately, which allows you to strike the iron while it’s hot.
• Cost Efficiency When Scaling: At $0.08-$0.13 per minute, Synthflow AI offers a cost-effective way to scale your calling capacity without breaking the bank.
• Easy No Code Deployment: The platform's user-friendly interface allows you to deploy AI voice assistants without talking to your developers.
• Seamless Integration with Third-Party Tools: Synthflow AI integrates smoothly with CRM platforms and other tools. It can transfer important contact data and conversation transcripts across your marketing and sales stack so your whole team is on the same page.

Getting Started With Synthflow AI

The core of Syntflow AI’s product is its assistants, which are automated voice assistants that can make or take calls.

Before you create your first assistant, I recommend setting up at least one phone number.

1. Setting Up a Phone Number

Phone numbers are essential for the Synthflow AI service. Without one, you can’t test, make, or receive calls. Also, keep in mind that each assistant requires a unique phone number, so if you plan to build five assistants, you need five phone numbers.

Currently, Synthflow AI supports numbers from the U.S., Canada, and Australia. Each phone number costs $1.50 per month in addition to your monthly subscription.

I found buying a phone number quick and straightforward. You simply select the number and pay for it:

Fortunately, you can connect local phone numbers from other countries through the Twilio integration. Just enter your Twilio Auth Token and SID, and the numbers will be populated in your Syntfhlow account, ready for use.

With your first virtual phone number purchased and set up, you're ready to create an assistant.

2. Creating Your First Synthflow AI Assistant

Regardless of which plan you're on, Synthflow AI allows you to create an unlimited number of assistants. This feature is quite useful as you can create as many test assistants as you need without worrying about plan limitations. However, you need to account for the costs of the additional phone numbers, as each assistant requires a unique phone number.

You can build an assistant from scratch, use a quick setup, or start with a predefined template.

As of this review, the platform provides only a limited selection of templates, mainly for recruiters, car dealers, and mortgage consultants. The quick assistant setup also offers just one option for an inbound receptionist.

Starting with a pre-made template is a great way to understand how to structure the assistant prompt (the instructions for your assistant). Even if your business is in a different niche, I recommend you start with a pre-made assistant and adapt it to your industry.

For instance, if you’re selling software, you can take Paul, below, who is made for real estate. With some changes to Paul’s phone script and agenda, you can easily adapt it to your needs.

Inbound and Outbound Assistants

Syntfhlow AI supports three main types of assistants:

• Inbound Assistants: These handle incoming calls from customers, such as support inquiries or general questions.
• Outbound Assistants: These assistants can initiate calls on your behalf, whether for cold outreach, follow-ups, or updates.
• Widgets: An embeddable chat widget for your website that enables real-time conversations and engagement directly with your visitors.

Now, let’s create a simple inbound assistant.

Configuring Your AI Assistant

The initial set of options for your assistant might look intimidating, but don't worry. Most of these features are easy to grasp.

Once you choose your assistant's name and avatar, you can select the voice engine and AI model. Synthflow AI supports most of the latest AI models, such as GPT-4o and GPT-4o-Mini, as well as its own unique LLM model.

Unlike other tools, such as Vapi AI, Synthflow AI doesn’t require you to set up the LLM model or pay extra for its subscription. The models are built into Synthflow and its pricing structure. How well the models work depends on how your prompt is written (more on that later).

You can further fine-tune the conversations by adding filter words, a custom vocabulary with words, and connecting your knowledge base and resources for the assistent to learn and use.

4. Giving Your Assistant a Voice

Synthflow AI's out-of-the-box AI voices are powered by ElevenLabs, the leading speech synthesis software. Thanks to advanced deep learning technology, they offer natural-sounding speech and sound remarkably lifelike without the robotic tone often associated with AI. You can have a test conversation here.

I found the voice of my assistants to sound almost perfect and, if not for the longer delays, almost indistinguishable from a real person.

That said, the longer pauses and the inability to interrupt the voice assistant mid-sentence reveal that you're speaking to an AI bot rather than a real human. So, if flawless human experience is your top priority, Synthflow AI might not be the best fit for you at this time.

Currently, Synthflow AI supports the following languages: English, Portuguese, Spanish, French, German, Italian, and Dutch. Of course, the platform allows you to select male and female voices, as well as a number of pre-set tones.

You can also create a custom voice clone by uploading five audio samples. Since Synthflow AI uses ElevenLabs, you can upload one of the voice presets available on the ElevenLabs marketplace. For example, if you need an Australian accent, you can upload a preset with that specific voice.

I was impressed by the additional options available for fine-tuning the voice, though I found the default settings to work quite well overall. The only option I was tempted to experiment with was the latency of the responses to reduce the awkward pauses during conversation. However, it’s worth noting that faster response times can sometimes compromise the quality of the answers.

Additionally, you can configure things such as the pause before the assistant speaks, how long the phone rings before the assistant answers, and the call duration limit (useful for when people forget to hang up the call, as you have a limited number of concurrent calls on your plan).

5. Creating and Structuring Your Assistant Prompt

Your assistant’s prompt is the set of rules and instructions it will follow when talking to people. If you've used ChatGPT in the past, you'll feel at home. That said, it’s best to start with one of the prompt templates as they are quite comprehensive. You can also use Synthflow’s “Prompt Co-Pilot” feature, a chatbot that hand-holds you through the process of building your prompt.

In your prompt, you want to mention things like:

• Assistant tone and personality
• The goal of the call and the assistant
• Conversational style
• Company information

Most importantly, you need to provide the most complete script instructions you can.

Below are the exact prompt structure and instructions I gave my sales assistant for a hypothetical project management cloud platform.

Introduction

This is where you explain who the assistant is and provide its main objectives. Here’s what I wrote:

Tone and Behavior

This is where you instruct your assistant on how to act. I provided the following:

Product Information

This is where you share how your product works. Here’s what I said about my hypothetical company:

Target Audience

This is the audience your bot will be speaking to. Here’s the detail I gave:

Value Proposition

Share the unique selling points (USPs) of your product or service. Here’s what I said (most companies will have more details to share):

Objection Handling Instructions

Write down the most common objections you usually hear on your phone calls. This helps train your AI assistant on these specifically.

Objection: “I’m already using a project management tool.”

Objection: “I’m new to project management software.”

Objection: “I’d prefer a self-hosted solution.”

Script Instructions

This is a step-by-step script on how a typical call should go. The best part about this is that you can copy and paste your existing sales script, and your assistant will follow it to the letter.

1. Initial Contact

2. Introduction and Initial Query

3. Highlighting Benefits

4. Organizing a Detailed Discussion

5. Confirming Phone Number

6. Closing and Follow-Up

One drawback I noticed with the prompt builder is that it was quite laggy and occasionally caused my browser to crash.

6. Testing Your AI Assistant

Before you deploy your new assistant, you want to test it. I found testing incredibly easy. You simply enter your phone number and click “Call me.”

The assistant will give you a ring, and you can talk to them freely and test different questions and answers. Alternatively, you can call the number yourself and start a conversation.

On the free trial, you get 15 minutes of free testing.

Once the call is over, you get a transcript, a recording, a summary of actions performed, and an analysis of the call.

All calls can be later viewed in an organized table:

To test your assistant through chat, click the “Chat” tab on the right sidebar and enter a prompt. The main benefit of chat testing is that it’s completely free but it’ll still show you how your assistant responds in certain situations.

Synthflow AI uses voice APIs to convert these prompt responses into spoken dialogue. In other words, what you see in your chat prompts is exactly what people calling your bot will hear on the phone.

Since test calls also cost credits (between $0.08 and $0.13 per call minute, depending on your plan), it's recommended that you conduct your more extensive assistant tests through text chat instead.

Here are some things you should consider testing. I’ll also show you how my AI assistant, Jordan, handled my inquiries.

Testing Your AI Assistant’s Introduction

This is where you test how your assistant starts a call.

The assistant’s introduction should differ depending on whether you have an outbound or inbound assistant. Since Jordan is an outbound assistant, I expected her to take the lead and start the conversation. However, that was not the case.

In the chat test, the assistant was waiting for me to start the conversation:

Attempting a phone call test didn’t make any difference.

I tried giving her more explicit instructions like: “Make sure you start the conversation first; do not wait for the person to talk.” It made no difference. No matter how I fine-tuned the prompt, Jordan still acted like an inbound assistant and didn’t initiate the call proactively.

Changing the LLM model also didn’t improve this.

I’m unsure if this was a bug in the testing process or a mistake in my settings, but the issue left me questioning the reliability of outbound assistants.

It’s worth noting that when evaluating these prompts, we're essentially testing ChatGPT (or any other LLM being used). As a result, any issues with answer quality are more likely tied to the LLM model itself rather than Synthflow AI.

Testing Your AI Assistant with Off-Topic Conversations

The next big thing you want to test is how the assistant handles off-topic conversations.

My first tests here failed as well:

But I quickly found that you must be more explicit in your instructions to keep your assistant in line. I added the following rule to the prompt:

This approach worked better, but I was disappointed that I had to be so precise with my prompts. Even then, some off-topic questions managed to slip through.

I expected Synthflow AI to include built-in rules for this within the pre-made templates. I know it’s possible because some of the walkthrough videos showed a bot handling off-topic questions much better than mine.

Testing Your Call Script

Last but not least, you want to test your on-topic script. My AI assistant, Jordan, handled this great without issues and seamlessly arranged a follow-up call to book a demo with me.

It’s still important to remember that this is a ChatGPT-based bot, and avoiding unwanted minor deviations or hallucinations from the script is impossible. For instance, I was expecting Jordan to mention our case study with IBM when talking about cost savings, but it was omitted. Because these bots aren’t totally reliable, it’s best to leave the handling of sensitive data, such as credit card details, to a human or secure interface.

7. Setting Up AI Assistant Actions

Apart from actual calls, your assistants can perform a number of handy additional actions:

• Send an SMS after the call to share follow-up information. Unfortunately, text messages don't currently support dynamic variables, so you're limited to a fixed text for all contacts.
• Book a call using Cal.com and GoHighLevel integrations.
• Transfer a call to a real person when the person requests it, or based on predefined characteristics.
• Extract call information to be displayed in the call summary. This is especially useful for outbound calls and lead qualification, where you need to skip through a large number of calls.
• Custom actions to connect with API and other advanced options.

8. Deploying Your Assistant

It’s time to get your assistant live! Synthflow AI offers a few options:

For inbound assistants, the easiest way to deploy is to share your phone number with your customers and leads. When they call the number, the AI assistant will answer.

For outbound assistants, you can import a CSV file with numbers and select a specific outreach cadence and time zone for calling. This feature is called “Batch Campaigns.”

If you’d like to automate additional actions across other tools, GoHighLevel and Zapier offer more advanced deployment integrations. The tool also supports Webhooks.

So far, we’ve covered how to create, configure, and deploy your first assistant in Synthflow AI.

In the next section, we’ll explore some of Synthflow AI’s standout features.

Key Synthflow AI Features

Book Meetings in Real Time

Syntflow AI’s assistants can book meetings in your calendar during phone calls so that you capture every opportunity. Currently, the platform supports integrations with HubSpot, Cal.com, ClickFunnels, Make, Zapier, and GoHighLevel. But chances are great that by the time you are reading this, there are more integrations available.

In my conversations with Jordan, the assistant was able to schedule a product demo call directly on the call instead of asking the person to leave a phone number and have a salesperson follow up to arrange a call. This saves one additional step in the sales process.

Transfer to Real Humans

Synthflow AI’s assistant can forward a call to one or more phone numbers whenever necessary. You simply specify the trigger words, for instance, “I want to talk to the manager.” In my opinion, this is a must-have feature as some people simply don’t like to talk to robots. You can also ask the assistant to share more information about the incoming transfer so the person handling the call can be more prepared.

When testing my assistants, the transfer feature worked smoothly, easily identifying my inquiries for a transfer, regardless of how I worded them: “Transfer me to a human,” “I want to talk to the manager,” etc.

Enrich Leads With Information Extraction

One of the post-call actions available to assistants is the ability to extract key information from the call. This can be used for lead qualification, customer research, or to gather more information on support issues.

You get the option to collect information in three different formats: Yes/no answers, single-choice answers, and open-question answers:

The answer to the question must be mapped to a unique identifier (think of it as a contact field). For instance, if you ask about the first name of the person in an open question, that identifier is “user_name.”

The platform also thoughtfully shows you what other assistants, if any, use that identifier:

This feature is critical for outbound calls and salespeople. It allows them to prospect cold leads and collect valuable information that can be later used in follow-up calls. Information such as company size, pain points, and objections can be extracted from the call and recorded in a CRM like HubSpot. This allows salespeople to prepare for calls much faster than by sifting through dozens of call transcripts.

Advanced Custom Actions

With Synthflow AI, you can design custom post-call actions to fit your specific requirements, business processes, and workflows.

These actions can range from collecting precise data and integrating smoothly with your preferred tools to triggering advanced workflows. Keep in mind this is an advanced feature that will require your developer’s input.

Below is an example of a custom action that does the following: “Gets the product details from Hubspot, querying the database using the product name.”

Assistant Teams

With Assistant Teams, you can create a whole fleet of AI assistants that work together.

Teams are a great way to combine assistants with different functions. For instance, you might have a lead qualification assistant who refers qualified leads to a real human and unqualified leads to a second assistant who can share automated information about your product or service.

You can specify when to transfer the person to another assistant and how long to wait before the transfer (to simulate a real transfer):

Workflows

Synthflow AI offers a visual workflow builder that allows you to automate a set of actions, similar to how you would use Zapier.

For example, let’s say you run a marketing agency and have Facebook ads promoting your content marketing service. When a lead enters their contact information through a Facebook ad, the Synthflow AI assistant can make an instant call to qualify them. If the lead is qualified, the assistant can add them to HubSpot CRM and create a task to follow up with them in a day. If not, the lead can be added to your email marketing tool for further lead nurturing.

This feature is only available on Pro plans and above, starting at $450/month.

Whitelabel Solution for Agencies

If you’re looking to start an AI-powered phone agency, Synthflow AI provides a flexible and fully customizable white-label option with advanced features to fit your needs.

Some of the white-label features include:

• Select which configuration options to display to your clients. For instance, you can hide the “prompt” section for your clients altogether and build your own prompts.
• Custom pricing structure
• Branded dashboard with logo, name, and custom domain
• Assign specific assistants, teams, workflows, phone numbers, and more to each sub-account

Overall, I was highly impressed by the attention to detail Synthflow AI has invested in its white-label feature.

Synthflow AI Pricing

Synthflow AI offers flexible pricing that scales with the number of call minutes. Overages cost $0.8-$0.13 per minute.

Final Verdict

The biggest challenge I faced with the Synthflow AI was getting the outbound assistants to deliver a proper proactive introduction on the call and initiate the script without input from the receiver. The assistant kept on being silent and acting like an inbound bot.

Another notable drawback was the effort required to create a robust prompt capable of handling off-topic questions. I wish the platform offered more comprehensive prompt templates with built-in rules for such scenarios. That said, if you're skilled at crafting prompts, you'll appreciate Synthflow AI's flexibility for designing your assistants.

Since my audience communicates via email or chat and doesn’t rely on phone calls, Synthflow AI isn’t a fit for my needs. Also, I still prefer genuine human-to-human communication and would avoid AI voice assistants unless the scalability needs or budget constraints require it.

That said, if you’re in a more traditional industry - like car rentals, real estate, mortgages, or any field that handles a high volume of calls - Synthflow AI could be a valuable asset to your business.

If you're ready to embrace AI-driven communication, you should definitely give Synthflow AI a go. It's easy to deploy and offers the customization features needed to build a capable AI voice assistant that can improve your processes and help you convert and retain more customers on autopilot.

Synthflow AI Alternatives

###Vapi AI Unlike the other tools on the list, Vapi AI is a solution geared toward developers (although it also provides a no-code dashboard). It's a voice AI API that allows you to build, test, and deploy voice assistants, as well as other text-to-voice solutions. Pricing starts at $0.05 per minute, which is significantly cheaper than the price of Synthflow AI. However, you must also pay additional costs for transcriptions, voice generation, LLM models (ChatGPT, for instance), and making the calls. This makes price calculations more complex but also flexible. That said, the customization options you have with Vapi AI allow you to bring its cost lower than Synthflow’s and let you optimize latency for faster response times.

###Califluent The first noticeable difference between Synthflow AI and Califluent is that Califluent supports 30+ languages, including Japanese, Indian, and Russian. Another benefit of Califluent is that apart from SMS messages, you can also send emails during or after the call. The biggest drawback of Callfluent is that it doesn’t support a white-label solution, so if you're an agency looking to set up AI call services, you would be better off with Synthflow.

###Bland AI The main difference between Synthflow AI and Bland AI is that with Bland AI you cannot upload your own custom voices or ElevenLab presets. A benefit of Bland AI is that you can purchase a custom number of credits for your calls vs. the predefined number of minutes that come with Syntfhlow plans.