Vapi

Vapi is infrastructure for voice agents that actually pick up the phone. Unlike ChatGPT Voice or Claude's conversational mode, this is built for production telephony: inbound support lines, outbound sales calls, appointment booking, voice surveys. The autonomy here is narrow but useful. You define a workflow (collect caller details, check availability, confirm booking), wire it to your backend via webhooks or function calls, and Vapi handles the conversational loop, interruptions, hold music, and transfer logic without you babysitting each turn. I used it to replace a scheduling hotline for a clinic. The agent asks for name and reason, checks a calendar API, offers slots, confirms via SMS. It handles interruptions well (caller changes their mind mid-sentence), stays on script, and logs structured data (name, phone, chosen slot) to a database. The alternative was hiring a receptionist or forcing patients through a clunky web form. Vapi sat in the middle: cheaper than a human, more forgiving than a form. The developer experience is solid. You get SDKs in Python, Node, and REST. Latency is low enough that conversations feel natural, not like waiting for a chatbot to wake up. You can inject custom voices (ElevenLabs, Play.ht) and tweak interruption sensitivity. Function calling works as advertised: the agent can query your CRM, update Notion, send Slack messages mid-call. Failure modes: it struggles with heavy accents or noisy lines more than a human would. If your workflow has complex branching (dozens of conditional paths), you will spend time debugging state machines. The pricing is per-minute, so a chatty agent on a long call adds up quickly. There is no free tier beyond a trial, so you are committing budget before you know if your use case fits. Compared to Bland AI (the closest competitor), Vapi gives you more control over the conversational flow and better docs. Bland is faster to spin up a demo but harder to customise deeply. If you are a developer who wants to own the logic and treat voice as another API, Vapi is the better bet. If you want a no-code builder, look elsewhere. This is not a general assistant. It will not plan your day or research competitors. It is a voice agent backbone: you bring the workflow, it brings the phone line and the conversational glue.