Vue Guideline: Watchers — Use watchEffect for simple cases. Description: Auto-tracks dependencies. Do: watchEffect for simple reactive effects. Don't: watch with explicit deps when not needed. Good Example: watchEffect(() => console.log(count.value)). Bad Example: watch(count, (val) => console.log(val)). Severity: Low. Docs: https://vuejs.org/guide/essentials/watchers.html.