You are building a structured data extraction system using Claude.

Retry-with-error-feedback is effective when the required information is available and the defect concerns representation. Options A, C, and D are correctable formatting failures: the model can flatten an object into an array, remove thousands separators and emit an integer, or convert a datetime into the required date-only format. The validation message supplies enough information to revise the output.

Option B is fundamentally different. The complete co-author list is absent from the model’s input and exists only in an external document. No number of retries can recover evidence that was never supplied. Repeated attempts may instead increase the probability of fabrication. Anthropic’s hallucination guidance recommends restricting responses to available documents, allowing the model to acknowledge missing information, and withholding or retracting claims that cannot be grounded in the source. ( https://docs.anthropic.com/en/docs/test-and-evaluate/strengthen-guardrails/reduce-hallucinations )

The correct response is therefore to return an explicit missing-data state, retrieve the external document through a tool, or route the record for enrichment. Retrying without changing the information boundary cannot solve the problem.

Current Anthropic Structured Outputs can eliminate many shape-related failures by guaranteeing JSON Schema conformance, but they still cannot create unavailable source facts. ( https://platform.claude.com/docs/en/build-with-claude/structured-outputs ) This distinction—format failure versus evidence failure—is central to reliable extraction architecture.

Official references/topics: Retry Boundaries; Missing Context; Grounded Extraction; Structured Outputs; External Data Retrieval.