The problem with the step planner approach in SK is that the entire agent's design and focus is to respond to a question it receives. It cannot in parallel engage in the conversation with the user. It can get lost in case an intent from the customer is expressed over multiple interactions in the conversation. This will be more problematic when the agent needs to also follow a business procedure. In my design the main agent's responsibility is to interact with user to achieve certain goal while it has access to a set of tools it can use in an intelligent way to solve a problem it encounters.