It depends on the source and destination. The trickiest case is when we're using browser agents for data entry. We can use the fact that we focus on repetitive tasks to our advantage - we know what sections of UI we need to check, and for what data. We can verify correctness by re-extracting data from the destination UI (via the DOM or OCR) and checking:

That all expected fields were entered correctly.

That no unexpected or extraneous data was added.

When we have access to a direct data source (like an API or file store), verification is simpler — we can do deterministic checks and directly confirm the values.

We're also building a validation library for common field types (dates, contact info, etc.) to enforce constraints and avoid propagating unverifiable or out-of-range values.