Function Calling
The ability for an AI model to invoke external tools or APIs during a conversation to take actions like booking appointments.
Function calling allows an AI voice agent to do more than just talk. During a conversation, the model can decide to invoke specific tools: checking a calendar for availability, creating a booking, looking up a contact record, or sending a confirmation email.
This works by defining a set of available functions with their parameters. When the model determines that an action is needed, it outputs a structured function call rather than a text response. The system executes the function and feeds the result back to the model.
Function calling is what makes AI voice agents genuinely useful for business workflows. Without it, an agent can only have conversations. With it, the agent can actually do things: book appointments, qualify leads against your criteria, and trigger downstream automations.