skills/trip-budget/references/budget-rules.md

# Budget rules

Include flights and baggage, lodging and taxes, intercity transport, local and airport transport, food and drinks, activities and admissions, tours and ferries, insurance when relevant, tourist/resort fees, connectivity, and contingency. When applicable include accessible vehicles, equipment baggage, medication storage/monitoring supplies, verified refrigeration, backup transport, and mobility/medical logistics contingency.

Do not multiply room totals by traveler count. Do not count a pass and covered tickets twice. State whether dining includes alcohol, tax, service, and gratuity. Use 5-10% contingency when the user has not set one, applied only to line items marked contingency-eligible.

Every item must use the base currency or provide an explicit dated conversion rate. Reject mixed currencies without conversion, negative costs or quantities, and non-finite values. Retain optional and excluded items separately instead of silently dropping them. A missing target remains null; do not invent a zero target or variance.

For each live price record travel dates, party size, fare/room/product type, cancellation basis, date observed, and whether availability was actually displayed. Dynamic prices remain observations, not promises.