Build a monitor that watches while you sleep

Build-along · ~14 min at your own keyboard

The simplest useful agent is a watcher: it checks a source on a schedule, compares what it finds against a threshold you set, and pings you only when something matters. A marketplace for a parcel under your price, a county portal for a new permit or planning-commission item, a rent-comp feed for a shift. The skill is not the checking, it's the THRESHOLD and the SILENCE. A monitor that alerts on everything is noise you'll mute; one that alerts on nothing is broken. Two build rules keep it honest. First, the threshold is explicit and yours ('asking under $X/acre AND legal access stated'), so you can tune it. Second, and this is the one everyone skips, the empty and error cases must be loud: if the source returns zero rows or fails to load, the monitor says so, because a watcher that silently reads nothing and reports 'all clear' is the exact failure that lets a deal or a deadline slip past. Schedule it with Claude's Routines or a cron; ship the logic working first, the scheduling is the easy part.

Your starter: Market monitor loop

Workflow steps

Make it yours: Name the two or three sources you actually read, set the hour it runs, and define what counts as a change worth a line.

MONITOR: [submarket], runs [weekday] at [hour]

1. Read [source 1: e.g. the offerings feed export] and [source 2: e.g. the public-notice page saved locally].
2. Compare with yesterday's snapshot at [path]. A change is: new offering, price change, status change, new notice.
3. For each change write one line: what, where, the source and the date it was read.
4. Anything with no source line is dropped, not guessed. No number without a source and a date.
   An offering with no asking figure on the page is written [SOURCE NEEDED: asking].
5. Write the day's lines to [path]/[date].md. If there are none, write 'No change' and the date.

Never fetch a page not on the list. Never email anyone.

The coach checks that what you paste back is your own work. The starter pasted back unchanged won't pass.

Do this

0/5

Share what happened

Paste your threshold rule, the loud-empty guard, one real alert it produced (and one quiet cycle where it correctly said nothing), and proof it ran on a schedule.