Definition of Ready
It is the responsibility of the product owner to add stories to the backlog. During the backlog refinement, the team has to provide feedback to get each story into an actionable condition. The stories at the top of the backlog, and that are candidates for the upcoming sprint, must be ready. Having a clear Definition of Ready (DoR) is important if you want to raise the productivity of your team.
The stories need to be immediately actionable. If they are not, how could one implement or test a feature? It must be clear what the objectives are, what needs to be done to make it happen, and what amount of work it takes. For example, the backlog may be filled with user feedback such as, "We want to able to create new invoices quicker." This statement clearly defines a problem, but if we want to work on it, we need more specific information. The team must be able to determine what needs to be done. If we could state that adding a button for creating new invoices to the main screen is the solution, then we can make an estimation for it and start working on it. A story that is ready is clear, concise, and actionable.