During September 2025, Marcy Calderon enhanced the hmrc/business-details-api repository by clarifying the timing for updating the Accounting Type endpoint. She focused on improving API documentation using YAML, ensuring that customers understood updates are permitted after the tax year ends and before the Final Declaration. Marcy’s work addressed customer confusion and reduced support queries by providing precise, traceable guidance without altering existing API behavior. Her approach emphasized clear communication and regulatory alignment, applying changes with minimal risk and full auditability. The project demonstrated her skills in API documentation and version control, delivering targeted improvements within a concise, feature-focused release cycle.