She built the tool that helped thousands of founders find each other. Then she found her own co-founder and started teaching machines to answer the phone.
Catheryn Li runs Simple AI, a San Francisco company with a blunt thesis: people hate calling businesses, the experience is terrible, and the fix is not a better hold queue. It is a voice agent that knows every product, every price, every objection, and never has a bad day. Her agents are trained on a company's best human reps. The company says they already outsell those reps by 30 percent on conversion and upsell.
The unglamorous part is the proof. Simple AI's early customers do not sound like a keynote slide. They sell steaks. They rent self-storage units. They quote home insurance. These are businesses that live and die by the phone, where a missed call is a lost sale and a bored rep is a leaking bucket. Li pointed the technology at exactly the places where a 30 percent lift is the difference between a good quarter and a great one.
The pitch she gives call-center directors is almost mischievous. Stop spending your day fixing your worst performers, she says. Start optimizing your single best one - and that best one is Simple AI. It is a quietly radical reframe of what a call center even is. Not a room of headsets to be managed, but one tireless top performer to be tuned.
She is not guessing at this market. She spent four years inside the machine that builds startups, watching which problems were real and which were theater.
Before Simple AI, Li spent four years at Y Combinator. She led the software team behind Startup School, the YC Library, and Co-Founder Matching - the tool that pairs up would-be founders who would otherwise never meet. There is a neat symmetry to it. She built the matchmaking software for everyone else, then quietly used her own time at YC to find Zach Kamran, who had been working on Bookface. The two noticed something odd in their 2024 batch: nobody was building for consumers. So they did.
The technical bar is unforgiving. A voice agent that pauses too long stops sounding human, so Simple AI holds end-to-end latency under 850 milliseconds - faster than the gap most people leave before answering a question. The system ingests a full product catalog: SKUs, metadata, pricing. It pulls real-time customer data mid-call to personalize the conversation and place orders. You can dial the agent's speed, pick its accent, choose its voice. The consumer-facing side will make calls on your behalf, wait on hold, and fight its way through phone trees in 15 languages across 33 countries.
The funding caught up with the work. In February 2026, Simple AI announced a $14 million seed round led by First Harmonic, with Y Combinator, True Ventures, and Massive Tech Ventures along for the ride. Li's own admission about the timing was disarmingly honest: the team had been so busy building for customers that they forgot to launch.
She holds degrees in computer science and mathematics from MIT. The technical foundation is not decoration - she led engineering teams long before she led a company.
She ran software for Startup School, the YC Library, and Co-Founder Matching. She watched thousands of founders pitch, fail, and pivot before she made her own bet.
When nobody in her YC batch was building for consumers, she and Zach Kamran went the other way. The whole company is one big bet against the crowd.
Studies computer science and mathematics. The technical spine of everything that follows.
Engineering roles at companies operating at the scale she would later need to understand instinctively.
Leads the software team behind Startup School, the YC Library, and Co-Founder Matching.
Co-founds the company with Zach Kamran and joins YC's Summer 2024 batch.
First Harmonic leads the round. The company that forgot to launch finally does.
A conversation breaks the moment one side lags. Simple AI engineers against that silence. Lower is better.
Illustrative. The point: stay under the threshold where a person notices the gap.
Before she had a co-founder, she built the software that helps other people find theirs - YC's Co-Founder Matching tool.
She once mentioned interviewing 100 candidates for a single role. She builds teams the way she builds product - exhaustively.
The consumer side of Simple AI will make calls on your behalf - sitting through hold music and phone trees so you don't have to.