# Rules Before Guesses
Source: https://humanspark.ai/frameworks/rules-before-guesses/

*If a rule can do the job, use the rule - save AI's best guess for judgement, language and interpretation.*

**When to use:** At the start of any build - to decide whether the task needs AI at all, or a rule does it cheaper.

Rules
the default

Same input, same output. Test it once, trust it after.

Spreadsheets, formulas, templates, scripts, pattern matching.

Best guess
the exception

Flexible, capable, never quite the same twice. Check it every time.

AI and LLMs.

> **Rules go stale:** A wrong guess gets noticed. A wrong rule repeats silently until somebody checks that reality has not moved on.

## Related frameworks

- [The Verification Tax](https://humanspark.ai/frameworks/verification-tax/) - why a guess costs more to run
- [Defensive Programming](https://humanspark.ai/frameworks/defensive-programming/) - when the guess has to run anyway