Writing effective monitoring criteria
How to phrase plain-English criteria so monitors catch what you want and stay quiet about what you don't.
The criterion is what separates a useful monitor from a noisy one. A vague criterion ("alert me on any change") generates too many false positives on a busy page. An over-specific criterion ("alert me only when the price is exactly $X.XX") misses the broader signal. This guide covers what makes a criterion work, the patterns that consistently fail, and how to debug a monitor that's too noisy or too quiet.
Be specific about the property, not the value
Strong criterion: "alert me when the price drops below $X." Weak criterion: "alert me when this page changes." The strong version targets a specific property (price) and a specific condition (below threshold). The weak version catches everything — banner updates, photo swaps, sidebar changes — and produces alert fatigue.
Use thresholds for numeric criteria
Numeric data (prices, stock levels, ratings) benefits from threshold criteria over absolute equality. "Alert me when the price drops below $20" is more useful than "alert me when the price is exactly $19.99" — the second almost never fires.
For content monitoring, name the topic
Strong: "alert me when a new article tagged with [topic] is published." Weak: "alert me when there's a new blog post." The strong version filters out off-topic posts; the weak version alerts on every publishing day. Specificity reduces noise.
Combine criteria when one isn't enough
Sometimes a single criterion catches too much OR too little. "Alert me when this product is in stock AND under $X" is two criteria combined — both must be true to fire. Most tools support this; the syntax varies.
Debugging a noisy monitor
If a monitor is firing too often: review the last 5 alerts. Are they on changes you actually wanted to catch? If not, the criterion is too broad. Tighten it. Common case: the page has rotating banners or timestamps that change every visit — the criterion needs to ignore those zones.
Debugging a quiet monitor
If a monitor never fires when you expected it to: induce the change manually (refresh the page in a different browser to see what actually shows up). Verify the property you're monitoring is actually rendered on the page. Some sites server-side-render in a different format than they client-side-render — what the monitor sees and what you see in your browser may differ.
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