A county benefits agent must check whether an ID number is valid against an eligibility API before continuing. Which technique should it use?

A county benefits agent that must check whether an ID number is valid against an eligibility API before continuing should use function-calling to validate that ID against the API. Validation is an authoritative system-of-record step; function-calling gives the model a structured tool to perform it and branch the dialogue on real results rather than appearances. That technique keeps benefits conversations grounded in eligibility systems. Using function-calling to submit the ID number to the eligibility API for intake skips the required up-front control and lets the conversation proceed without proving eligibility before continuing. Using function-calling to fetch eligibility details for the ID number from the API may surface information linked to that ID but cannot confirm it is a real, currently valid record the way a validation call does. Using function-calling to validate the ID number format with the eligibility API only verifies syntax and leaves the required authoritative check undone, letting the conversation proceed without proving eligibility prerequisites now. On the exam, function-calling against the eligibility API is the validation technique; distractors use function-calling to submit the ID for intake, fetch eligibility details for the ID number, or check only ID number format without validating the ID against the API. Caveat: handle API denials and timeouts explicitly—do not treat tool failure as a valid ID, and avoid leaking whether an ID exists beyond what policy allows. Operational check: submit valid and invalid IDs in test, verify the eligibility API tool is called, confirm the dialogue blocks progression on invalid/failed checks, and ensure no path awards benefits language without a successful validation result.