Move deterministic loop steps into code

These examples and illustrative results are independently authored teaching materials, not measured model results.

Use case

An agent repeatedly normalizes invoice currencies/totals and interprets unclear descriptions. Teaching I1=usd/100 cents, I2=USD/250 and I3=EUR/300; allowed currencies are USD/EUR with separate sums and no exchange. I2 service/I3 fee classification needs contract context.

Mechanism

Map call-site responsibilities and identify outputs fully determined by complete inputs/rules. Move formatting/filtering/arithmetic into tested code with validation. Retain genuine interpretation with necessary evidence. Structured fields can still require policy judgment; shape alone does not justify deleting the model step.

Bad example

Ask the model to normalize/sum each fixture row repeatedly, then force business classification from service/fee without checking policy/contracts.

Good example

Use ordinary code for permitted-currency normalization, integer-cent validation and per-currency totals: USD=350, EUR=300, without mixing/exchange. Separately handle service/fee classification with contract evidence, preserving missing-context uncertainty. Record replaced versus retained call responsibilities and inspect deterministic results/residual inputs.

Why the change matters

Code makes fixed invariants inspectable while responsibility separation keeps real ambiguity from becoming guessed hardcoded policy.

Observable expectation

Compare USD 350/EUR 300 and invalid-currency/noninteger errors. Contract-free classification stays unknown; arithmetic success does not establish classification.

Inspect complete call mapping and retained judgment/error handling. No real financial records are processed.

Limits

Determinism requires complete policy/input; real precision/limits/categories follow the project. Source one-model-call advice is not a universal call count. This fixture measures neither cost nor effect.