Monotonic constraints

When might a monotonic constraint improve a boosting model, and what is the risk of imposing it on a financial feature?

A justified directional relationship can reduce model flexibility and improve stability in sparse regions. But a globally monotonic effect may be economically false, change with regimes or interact with other features. Validate constrained and unconstrained models under the same chronological protocol and inspect where the constraint binds. Economic intuition is a hypothesis to test, not proof of a permanent global shape.