price-watch

Price Watch

Set it up as a plan, not a reminder

A watch is a plan step parked on a condition. plan_start with the goal in the owner's words, then plan_add_step with:

{"kind": "page_number", "url": "<product page>",
 "pattern": "Rp ([0-9.]+)", "op": "below", "value": 9000000,
 "every_seconds": 3600}

and notify: true on that step — a price crossing the line is exactly what the owner asked to be interrupted for.

Three details decide whether this works:

• Watch the product page, never a search or category page. Search results reorder, and the number you captured yesterday belonged to a different item.
• Check the pattern once by hand with fetch_page before parking the step. A pattern that matches nothing waits forever and reports nothing, which is indistinguishable from a price that never moved.
• Give the plan an expiry. Most watches stop being wanted long before they stop running.

What counts as worth saying

A threshold, not a change. Marketplace prices jitter by a percent or two daily, and a message for each jitter is a message the owner turns off — after which the real drop arrives in a muted channel.

• If the owner named a target price, that is the threshold.
• If they said "let me know if it gets cheaper", propose one — around 10% below today's price is a starting point, and confirm it rather than guessing silently.
• Fire on crossing, not on being below. The condition fires once, the step runs once, and that is the end of it unless the owner asks for another watch.

When it fires

The condition hands you what it saw — the price, and where. Do not re-fetch to find out why you woke; the page may have changed in between and you would report something the owner was not alerted about.

Say: the price now, the price when the watch started, the threshold, and the link. Then stop. A watch that fires and then keeps watching without being asked is a subscription nobody agreed to.

When it does not fire