You gotta mentally work through that idea towards implementation, carefully assessing the consequences for other members of the team (dev, design, QA, doc, PM, etc.) and overall impact on the product design direction. Consider the following questions:

What’s the impact on aesthetics? Does it deviate from pre-set styles (like CSS)? Does it introduce new (undesirable) modalities or unfamiliar behaviors inconsistent with the rest of the product? Does it interrupt the natural workflow? Is it something “cool” for the sake of hipness without real benefit to solving a user’s problem? Is it introducing scope creep given the current cycle/release? (ie, being a consultant it’s important to be mindful/respectful of the client’s situation, helps build cred and relationship)