product-price-monitor

Define a watch contract with the exact item variant, source URL, and alert condition, then fetch a baseline with web_extract. Schedule a cronjob tick that re-fetches, normalizes the all-in price, and compares against the threshold stored in a state file.

Pin the exact route, dates, travelers, cabin class, and refundability terms in the watch contract. Run scheduled fetches that normalize base fare plus mandatory fees, convert currency with a timestamped rate, and alert only on qualifying drops or availability changes.

Alerts mismatch when the watch contract does not pin size, seller, cabin, dates, or room terms precisely. Record product IDs, variant attributes, and acceptable substitutes during setup so two variants cannot be confused at fetch time.

Store the last good observation and last alert fingerprint in the state file under ~/.hermes/price-watches/. Replaying the same offer sends no second alert, and a cooldown window suppresses near-duplicate triggers within the configured interval.

Avoid this approach for one-off current-price lookups, which are faster via direct web_search or web_extract. Scheduled monitoring is also inappropriate when site terms prohibit polling or when rate limits would cause blocking.