Validation, retry and feedback loops

Key points

1. 1Retry with error feedback: the follow-up includes the original document, the failed extraction and the specific validation errors ("line_items sum to 1,180.00, total_amount is 1,280.00"). Re-sending the same prompt just rolls the dice again.
2. 2Retries fix format and structural errors (a date not in ISO format, a value in the wrong field). They cannot fix missing information: if the value is absent from the source or lives in another document, return null, flag it for review and stop retrying.
3. 3Tool use with a JSON schema eliminates syntax errors (broken JSON, wrong types). Semantic errors remain: line items that don't sum to the total, a value placed in the wrong field. Catch them with validation in code.
4. 4Self-correction: extract calculated_total alongside stated_total, and add a conflict_detected boolean when the source contradicts itself. Discrepancies become visible instead of silently "fixed".
5. 5Feedback loop: add a detected_pattern field to every finding, so dismissed findings can be grouped by the construct that triggered them and the noisy criteria refined.