Learn in the textbookBusiness Requirements Definition — Functional / Non-functional Requirements and Agreement
DefinitionAgreement on requirements (要件の合意) means confirming the compiled requirements with stakeholders such as the user department, with both sides accepting that work will proceed on that basis, so that the requirements become final.
ExplanationWhat has been agreed is recorded in a document such as the requirements specification (要件定義書), and later phases proceed on that basis. Moving into development without agreement makes it likely that mismatches with actual business practice surface after completion and force rework.
AnalogyIt is like a custom-built house: the owner and the builder meet repeatedly to settle the specifications, and finally the owner accepts the content and signs. After signing, construction follows those specifications.
Memory hookThe first character of 合意 (agreement) means to bring together. The builders and the users first bring the content together, and then the users' manager approves it to make it final.