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Zero-Shot Prompting

Zero‑Shot Prompting — A Clear, Step‑by‑Step Guide

Learn how to write one simple instruction that a model can follow without any examples. We will define each word, show easy patterns, and practice with small tasks.

1) What is Zero‑Shot?

Zero‑shot prompting means you write an instruction and the model completes the task without seeing examples for that task. The instruction must be clear and complete.

Goal: One good instruction that tells the model what to do, any limits, and the shape of the answer.

2) Building Blocks (Simple Definitions)

Instruction: The main command. It tells the model what to do. Example: "Classify the review as positive, negative, or neutral."

Input text (or data): The content the model must use. Example: "The camera is great, but delivery was late."

Constraints (rules): Limits that keep answers consistent. Example: "Return only one label. No explanation."

Output format: The exact shape of the answer. Example: { "label": "<positive|negative|neutral>" }

Role (optional): A short role that sets behavior. Example: "You are a precise data extractor."

Acceptance checks (optional): How you will check success. Example: "Answer must be valid JSON and use ISO dates."

3) A Simple Recipe

  1. Write the instruction in one clear sentence.
  2. Add 1–3 constraints (labels, word limit, “no explanation”, etc.).
  3. Specify the output format (often JSON).
  4. Paste the input text under a clear heading like Text:
  5. (Optional) Add a short role and acceptance checks.

4) Prompt Patterns

Pattern A — Instruction + Constraints + Output
Instruction: Classify the sentiment of the review as "positive", "negative", or "neutral".
Constraints: Use exactly one label. No explanation.
Output: {"label":"<positive|negative|neutral>"}
Text: "The camera quality is fantastic and battery lasts all day."
Pattern B — Role + Task + Checks
Role: You are a precise data extractor.
Instruction: Extract the person's full name and date from the text.
Checks: Return JSON only. Use ISO date if present, else null.
Text: "I, Rakesh Babu, met on 14 Aug 2024 in Chennai."
Pattern C — JSON‑Only Guardrail
{"role":"system","content":"Respond only in valid JSON with keys: label, confidence. Confidence in [0,1]. Refuse non‑JSON."}

5) Fully Worked Examples

Needs Improvement (Why it is weak)
"Tell me if this review is good or bad."
  • No label set (What counts as "good"?).
  • No format (How should the answer look?).
  • No constraint (The model may ramble).
Good Prompt (Clear and Checkable)
Instruction: Classify the sentiment as "positive", "negative", or "neutral".
Constraints: Use exactly one label. No explanation.
Output: {"label":"<positive|negative|neutral>"}
Text: "I waited long for support, but the agent fixed my problem quickly."
Why it is good: clear labels, strict output, and a rule to avoid long answers.
Example — Information Extraction
Instruction: Extract fields as JSON: {"name":string,"meeting_date":"YYYY-MM-DD"|null,"city":string|null}. Return JSON only.
Text: "I, Rakesh Babu, met on 14 Aug 2024 in Chennai regarding onboarding."
Expected Output
{"name":"Rakesh Babu","meeting_date":"2024-08-14","city":"Chennai"}
Example — Polite Rewrite
Instruction: Rewrite the sentence in a polite professional tone in 20 words or fewer. Return only the rewritten sentence.
Text: "Send the report now. You're late again."
Expected Output
"Please share the report as soon as possible; let’s align on timings to avoid future delays."

6) Do / Don’t (with reasons)

DoDon’tReason
State one task clearly. Mix multiple tasks ("Summarize and translate"). Models perform better with focused instructions.
Define the output format. Assume the model knows your schema. Explicit formats prevent guesswork.
Add constraints for length or tone. Allow unlimited text. Constraints reduce rambling responses.

7) Practice Tasks

  1. Create a zero-shot prompt to categorize bug reports into: UI, Backend, Data, Other.
  2. Write an instruction that extracts phone numbers from text and outputs them as JSON array.
  3. Design a prompt that rewrites a paragraph for a 5th grader in two sentences.

8) Glossary

  • Constraint: A rule to follow (length, tone, format).
  • Schema: Structure of the data you expect.
  • Guardrail: A safety instruction that prevents undesired outputs.

9) Summary

Zero-shot prompting is about giving the model a single, complete instruction. Define the task, constraints, format, and the input clearly. Practicing with real tasks will make your prompts more reliable.