What automation tool should be used for quick and responsive actions based on immediate prospect behavior?

The best choice for quick and responsive actions based on immediate prospect behavior is the completion action. Completion actions are triggered automatically when a specific action occurs, such as a prospect submitting a form or clicking a link in an email. This allows for immediate and context-sensitive responses, such as sending a follow-up email, assigning a lead to a sales representative, or moving a prospect to a different stage in the sales process.

While other options like dynamic lists and automation rules have their place in managing prospects and segmentation, they may not respond as quickly or specifically to immediate actions. Dynamic lists update automatically based on specified criteria, providing a broader segmentation of prospects rather than responding to individual behaviors. Similarly, segmentation rules are designed to categorize prospects but do not initiate immediate actions based on real-time interactions. Therefore, completion actions are specifically designed to handle immediate behaviors, making them the most appropriate tool for this scenario.