# Diagnostic Hints


Diagnostic hints are stable labels for recurring checker and validation
failures. When an error includes a `Hint::<key>` token, the matching
page explains what the key means and where to start debugging.

Use this section when the raw error is too local and you need the
larger shape of the failure: which kind of invariant was violated,
what the checker was trying to establish, and what sort of change is
usually relevant.

Each hint page also points back to the source location that emits the
hint.