Let's say after the lead answers a question, he suddenly ask some random question like how much does it cost, are you an AI. Where can we put these generic commonly asked questions into the workflow?

Use a knowledge base with the Query Tool, set up conditional branches and interruption handling, and write prompts that briefly answer and redirect back to the main flow.

can I call the query tool inside workflow?

Yes, you can integrate the Query Tool into your workflow either through the Dashboard by adding and configuring it visually, or by using your API for more flexibility and control. Both methods allow you to set up the tool to query a knowledge base and invoke it within your workflow..

how can I make use of the interruption handling in workflow? Any specific documentation on this topic?

Use features like CallbackStep to pause and resume conversations, and speech configuration settings to fine-tune responsiveness.. https://docs.vapi.ai/how-vapi-works