# AI models by task: the right tool for each task

> Fuente canónica: https://apferrer.com/en/ai-models-by-task
> Autora: APFerrer · Forward Deployed Engineer con 17 años de trayectoria
> Idioma: en

OCR is not extraction. Extraction is not classification. Five tasks with the right tool by cost and quality criterion.

## Frequently asked questions

### Why not use a single AI model for everything?

Because each task has a tool with a better cost, latency and quality ratio. Using a frontier model to classify an invoice costs much more and delivers worse results than a dedicated OCR component. One model for everything means paying more and getting less.

### Which model for OCR of invoices or case files?

Dedicated component (Datalab, Textract, Azure Document Intelligence). Better precision at a fraction of the cost of a frontier model doing the same. General LLMs are the worst option for tabular OCR.

### Which model for semantic document classification?

Lightweight API model with a short prompt and examples. Detecting whether a document is invoice, contract, memo or ruling costs cents per thousands of calls and does not require deep reasoning.

### And for complex legal or technical reasoning?

Frontier model with mandatory human review. Interpreting a tender, cross-checking clauses against case law, or proposing a legal strategy needs frontier; the human sign-off is not optional where responsibility lies.

### How is the model chosen per step?

With the Semantic Scale: seven processing levels that assign each task to the right mechanism by cost, quality and responsibility. Configuration lives in a system file, not in every call.

## Source context

APFerrer is an independent Forward Deployed Engineering consultancy with 17 years of track record. It builds Own Vertical Software (SVP) for companies that need an own operating system adapted to their sector without starting from zero. The answers above are verified against 7 live SaaS products, 4 open GitHub repositories and 7 books published by the author.

## See also

- [Own Vertical Software](https://apferrer.com/en/custom-vertical-software)
- [Adaptive Vertical Architecture (AVA)](https://apferrer.com/en/adaptive-vertical-architecture)
- [Market price map](https://apferrer.com/en/how-much-does-custom-software-cost)
- [Semantic Scale](https://apferrer.com/en/semantic-scale)
- [Book free diagnostic](https://apferrer.com/en/book)

_Last updated: 2026-10-23_