Launch HN: Retell AI (YC W24) – Conversational Speech API for Your LLM

This is very interesting. One thing I wondered about the per-minute pricing is how to keep a phone agent like this from being kept on the phone in order to run up a bill for a company using it. It'd be very inexpensive to make many automated calls to an AI bot like the dentist receptionist in the demo, and to just play a recording of someone asking questions designed to keep the bot on the phone.

As a customer of a service like Retell (though of course not specific to Retell itself), how might one go about setting up rules to keep a phone conversation from going on for too long? At 17¢ per minute, a 6-minute call will cost just over $1, or about $10 per hour. Assuming the AI receptionist can take calls outside of business hours (which would be a nice thing for a business to offer), then such a malicious/time-wasting caller could start at closing time (5pm) and continue nonstop until opening time the next day (8am), with that 15 hour span costing the business $150 for billable AI time. If the receptionist is available on weekends (from Friday at 5pm until Monday at 8am), that's a 63-hour stretch of time, or $630. And if the phone system can handle 10 calls in parallel, the dentist could come in Monday morning to an AI receptionist bill of over $6,300 for a single weekend (63 hours × $10 per hour × 10 lines).

This is in no way a reflection on Retell (I think the service is compelling and the usage-based pricing is fair, and with that being the only cost, it's approachable and easy for people to try out). The problem of when to end a call is one I hadn't considered until now. Of course you could waste the time of a human receptionist who is being paid an hourly wage by the business, but that receptionist is going to hang up on you when it becomes clear you're just wasting their time. But an AI bot may not know when to hang up, or may be prevented from doing so by its programming if the human (or recording) on the other end of the line is asking it not to hang up. You could say it shouldn't ever take more than five minutes to book a dentist appointment, but what if the person has questions about the available dental procedures, or what if it's a person who can't hear well or a non-native speaker who has trouble understanding and needs the receptionist to repeat certain things? A human can handle that easily, but it seems difficult to program limits like this in a phone system.

Is there societal value that this product is harming?

What's the difference between your product and Gridspace's? I get the sense that your offering is more developer-focused, but I'm curious if there are any technical differences.

It might ask for permission to use the microphone. If you can't find it, try going to the website's homepage, where you can enter your phone number to receive a call.

This can be handled with function calling and other features in LLM. We support the input signal of closing the call, and you can have your rule-based (timer) system or LLM-based end call functionality and use that to hang up.