When to use it
Use it when you're handed a deadline that can't be met without cutting something. Say what it would take to hit the date. Now the person asking knows the trade-off and can choose: keep the date and cut scope, or keep the scope and move the date.
Example
Manager: “We need this by the 15th.”
You: “That deadline is tight. To hit it, we'd need to cut the extras, like the export feature.”
Manager: “Let's cut export for now.”
In an email or Slack message
In email: “The 15th is doable if we drop the export feature. With export, the realistic date is the 22nd. Which would you prefer?” Two clear options get a fast decision.