Zero-shot means asking for the task without showing a single example.
You describe what you want and rely on what the model already learned.
For common tasks described clearly this works remarkably well.
Translation, summarisation, classification into obvious categories and rewriting all suit it.
It is the cheapest option, since no example tokens are sent or billed.
It is also the fastest to write, so it is the right first attempt.
It weakens when the task has an unusual output format.
The model will produce something reasonable that is not quite the shape you needed.
It weakens again when your categories are specific to your business.
Urgent, blocked and waiting mean particular things in your team that the model cannot guess.
Edge cases are where it fails most quietly, since the common cases keep working.
The upgrade path is to add two or three examples and become few-shot.
Adding examples of the edge cases specifically is usually worth more than adding more examples.
Larger and instruction-tuned models are markedly better at zero-shot than base models.
Always try zero-shot first, then add examples only where it measurably fails.