Make the assumption explicit
A useful scenario names the shock, the time horizon, and what stays constant. Compare a broad market decline with an asset-specific decline rather than treating them as the same event.
Measure portfolio effects
Review estimated change in value, concentration, drawdown, and available liquidity. The purpose is to identify pressure points and possible responses, not to produce a precise prediction.
Keep the result reviewable
Store the inputs and timestamp with the output. When market data or holdings change, the earlier scenario should remain understandable rather than being overwritten by the newest result.