With the OpenAI Realtime API, developers can build speech-to-speech applications that interact directly with a generative AI model by speaking to it. The API enables the creation of tools that the model can use to execute functions and extend its capabilities. A developer built an example using Twilio's platform, connecting a phone call to GPT-4o with Node.js or Python, but wanted to explore more possibilities. To achieve this, they extended the original assistant into an agent that can choose to use tools to augment its response. The agent uses retrieval-augmented generation (RAG) with Astra DB to gather up-to-date data and store it in a database. This allows the model to search the database for additional information, providing more accurate responses. The developer created a tool that enables the model to perform vector searches against the collection, returning relevant text chunks as context. The agent now provides a new way to connect with the Taylor Swift bot, enabling users to chat and ask questions about the singer-songwriter using voice or phone calls. The combination of Twilio, OpenAI, and Astra DB creates a powerful agent that can leverage tools like RAG to provide more accurate responses.