How do you use one prompt to extract multiple fields at once vs many separate prompts?

medium

Answer

$Multi-field: single prompt asks for a JSON with all fields at once \to 1 API call, cheap, but errors in one field can bleed into others; long output = more room for hallucination.$
$Per-field: separate prompt per field \to K API calls, higher cost + latency, but each prompt is simpler and mistakes are isolated.$
$Best practice: multi-field for correlated fields (structured entity extraction), per-field for critical / independent fields (safety flags).$
$Combine with constrained decoding for reliability.$

Check yourself — multiple choice

Always split per-field
Multi-field: cheap but risk of bleed; per-field: costly but isolated errors — pick per correlation and criticality; add constrained decoding
Always multi-field
Same cost either way

Multi-field vs per-field: trade-off between cost/latency and error isolation.

#prompting#production#cost

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