The limit of the agent is your imagination. Ok, they may stutter and need fine-tuning but that's how playing with anything goes. Between the Vapi API, the inbuilt tools and the ability to easily add custom knowledge just using an assistant can get you far. My current approach has been to get a quick well tuned POC via an assistant and some knowledge base work. The flow has gotten pretty good but I'd love to move to a workflow and compare it with the assistant made via promoting, meta prompting and slowly understanding VAPI.. My only annoyance is the lack of documentation. The documentation on tools, knowledge base and the prompting guide could be better. The community and ChatGPT/gemini have been great help though along with just exploring the dashboard and API