A Reason Code Without a Source Is Half a Diagnostic

A failure message can be technically correct and still be frustratingly incomplete. Consider a timeout. It tells us something important about the failure mechanism, but not which operation encountered it. Adding the complete request target might answer that question, yet it can also expose identifiers, query parameters, access material, or other data that never belonged in a broadly visible diagnostic record. A safer middle ground is to give failures two separate coordinates: a reason code that explains how the operation failed, and a bounded operation label that explains where it failed. That distinction makes diagnostics more useful without turning failure handling into an accidental data-exposure channel. A reason code is not a location Reason codes describe failure mechanics. Generic examples might include deadline , cancelled , unauthorised , or invalid_response . These codes are valuable because they let systems group similar outcomes. A dashboard can count deadline failures across operations, while application logic can decide whether a particular reason is retryable. What a reason code cannot reliably explain is the operation being attempted. A deadline during a summary read may require a different investigation from a deadline while assembling a detailed response. Combining both meanings into one free-form message makes failures harder to query and encourages presentation text to become an informal data model. Model the two coordinates separately A deliberately generic, invented C# model might look like this: public enum OperationArea { Summary , Detail , Archive } public sealed record FailureDetail ( string ReasonCode , OperationArea ? Area = null ); The reason remains suitable for classification. The operation label adds location without carrying an unrestricted request value. An enum is not the only option. A validated value object or centrally managed set of constants can work too. The important constraint is that labels come from a small, reviewed voca