Before assembling a team and starting work on a project, it is crucial to define the project scope with stakeholders. This ensures that there is a clear understanding of what the project will deliver, the boundaries of the project, and the criteria for its success. Defining the scope provides a baseline for making decisions about what is and is not included in the project's deliverables and is essential for project planning. Formal acceptance of the scope from stakeholders is also necessary to confirm that the project will meet their needs and expectations. This aligns with the best practices in business analysis, which emphasize the importance of stakeholder engagement and requirements management to ensure successful project outcomes.
References: PMI's 'A Guide to the Project Management Body of Knowledge' (PMBOKGuide) and 'The PMI Guide to Business Analysis', which includes 'The Standard for Business Analysis'.