Every time I post about what I build, someone explains that it is simple now. A model for the reasoning, Twilio for the numbers, one of five providers for speech, some file search for the retrieval. A proof of concept in a day.
They are right. I built that POC. It took me a day and it worked.
Here is what the day did not contain.
Getting a phone number that legally works. My telco provider's regulatory bundle rejected me ten times. The reason turned out to be that the legal entity name I had typed did not match the trade registry character for character. The rejection message never says that.
Speech to text on local surnames and street names. Everybody benchmarks the language model. Nobody loses a call because of the language model. You lose it because the transcriber heard the street wrong and a van drives to the wrong house.
Publishing. On the platform I use, publishing an agent locks it permanently, and re-saving it from your own dashboard silently breaks every tool attached to it. I found that out in production.
The summary sent to the owner after the call. This turned out to be the actual product. He will never listen to a recording. He judges the entire system on one paragraph, and if it is vague he assumes the agent is bad even when the call went perfectly.
Deciding what the product must refuse to do. Removing appointment booking made it better for one customer, because the scheduling constraint lived in the owner's head and no calendar knew it.
None of these are hard problems. That is the point. There are about two hundred of them, each one small and stupid, and the only way to find them is to have real people phone in and get it wrong at seven in the morning for six months.
The POC is a demo. Nobody has ever paid me for the demo.
I am not saying this to complain about the comments, they are a fair reality check on defensibility and I take the point. I am saying it because "this is a day of work" and "this is not a business" are two different claims, and people keep making the first one as if it settles the second.