Creating a mockup is essential for building Conversational AI agents to visualize the design, provide feedback, and ensure efficiency. A high-fidelity mockup should account for node types, variable accountability, and user result satisfaction. Various tools such as Miro, Lucidchart, Draw.io, and even pen and paper can be used to create mockups. Starting with a key is crucial, which involves breaking down the functionalities of the agent into its components. By following this approach, designers and stakeholders can agree on the possible outcomes and flows, ultimately saving time and resources in the long run.