# Decision matrix: method, cost, latency, and setup

| Method | When? | Cost profile | Latency profile | Setup expectation | Boundary it does not solve |
| --- | --- | --- | --- | --- | --- |
| Prompt engineering | Instructions, output format, or task definition is insufficient | Low setup; per-call token cost remains | No extra retrieval; longer prompts may still add time | Hours to a few days | Does not supply current enterprise facts, authorization, or write deduplication |
| RAG | Answers need current, authorized source evidence | Indexing + storage + retrieval + inference | Adds retrieval/reranking; measure it | Days to weeks | Does not guarantee source correctness or atomic writes |
| Fine-tuning | Labeled examples address repeated behavior/format errors | Data preparation + training + evaluation + inference | Model-dependent; not automatically faster | Weeks, longer without usable data | Not a live inventory/pricing authority or transaction deduplicator |
| Agentic workflow | Tools, multistep decisions, and enterprise actions are required | Orchestration + tools + retries + review/operations | Multiple calls and queue time; requires a run budget | Weeks to months, depending on ERP contracts | Does not provide safe writes without policy, idempotency, outbox, and reconciliation |

Planning ranges, not benchmark results or quotations.