Imagine a project where the interface to be delivered has been locked down 90%, and you are already in possession of a solid architectural design. Would an agile methodology still offer any value in this situation? It seems to me that agile methodologies (and I'm thinking Scrum), offer most value where there is a high degree of uncertainty about the requirements. 
Is an agile methodology appropriate in this situation?
project management;agile;scrum
Would an agile methodology still offer any value in this situation?Yes.It seems to me that agile methodologies (and I'm thinking Scrum), offer most value where there is a high degree of uncertainty about the requirements.Also true.Here's the point.  Agile is a life-style.  Read the Agile Manifesto a few times.  You are not prohibited from locking down the interface.  You are not stopped from using a solid architectural design.You are encouraged to interact, create software, collaborate and respond to change.You are not prohibited from doing design work.The point is to avoid hyper-complex, fussy processes and procedures for change control.  Avoid the busy-work of writing long, detailed specifications when a conversation would do.   