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Prompt Engineering

vibeeval/prompt-engineering

Prompt templates, few-shot examples, chain-of-thought, structured output, evals

1k tokens
context cost
the whole folder, loaded on every use
1
files
instructions only
0
copies elsewhere
how many repositories repackaged it
521
stars on the repo
on the repository, not the skill itself

Install

one command, takes just this skill from the repository
npx skills add https://github.com/vibeeval/vibecosystem --skill prompt-engineering

The instruction itself

13 sections, as written by the author

Prompt Engineering

Prompt Templates

System Prompt Structure

SYSTEM_PROMPT = """You are a {role} specialized in {domain}.

## Task
{task_description}

## Rules
{numbered_rules}

## Output Format
{format_spec}

## Examples
{few_shot_examples}
"""

Few-Shot Template

def build_few_shot_prompt(task: str, examples: list[dict], query: str) -> str:
    prompt = f"Task: {task}\n\n"
    for i, ex in enumerate(examples, 1):
        prompt += f"Example {i}:\nInput: {ex['input']}\nOutput: {ex['output']}\n\n"
    prompt += f"Now process:\nInput: {query}\nOutput:"
    return prompt

# Usage
examples = [
    {"input": "The food was great", "output": '{"sentiment": "positive", "confidence": 0.95}'},
    {"input": "Terrible service", "output": '{"sentiment": "negative", "confidence": 0.90}'},
    {"input": "It was okay", "output": '{"sentiment": "neutral", "confidence": 0.70}'},
]
prompt = build_few_shot_prompt("Classify sentiment as JSON", examples, "Really loved it!")

Chain-of-Thought Patterns

Explicit CoT

Analyze this code for security vulnerabilities.

Think step by step:
1. Identify all user inputs
2. Trace each input through the code
3. Check if any input reaches a sensitive operation without sanitization
4. For each vulnerability found, classify severity (critical/high/medium/low)
5. Suggest a fix for each vulnerability

Code:
{code}

Self-Consistency (Multiple CoT paths)

import json
from collections import Counter

async def self_consistent_answer(question: str, n_paths: int = 5) -> str:
    answers = []
    for _ in range(n_paths):
        response = await llm.generate(
            f"Think step by step and answer: {question}\n\nFinal answer:",
            temperature=0.7,  # Higher temp for diversity
        )
        final = extract_final_answer(response)
        answers.append(final)

    # Majority vote
    most_common = Counter(answers).most_common(1)[0][0]
    return most_common

Structured Output

JSON Mode with Schema

from pydantic import BaseModel, Field
from openai import OpenAI

class CodeReview(BaseModel):
    issues: list[dict] = Field(description="List of issues found")
    severity: str = Field(description="Overall severity: low|medium|high|critical")
    summary: str = Field(description="One-line summary")
    suggestions: list[str] = Field(description="Improvement suggestions")

client = OpenAI()

response = client.beta.chat.completions.parse(
    model="gpt-4o",
    messages=[
        {"role": "system", "content": "Review code and output structured analysis."},
        {"role": "user", "content": f"Review this code:\n```\n{code}\n```"},
    ],
    response_format=CodeReview,
)

review = response.choices[0].message.parsed

XML Tags for Claude

<task>Analyze the following error log and extract structured information.</task>

<rules>
- Extract timestamp, severity, service name, and error message
- Classify root cause category
- Output in the specified XML format
</rules>

<input>
{error_log}
</input>

<output_format>
<analysis>
  <timestamp>ISO 8601</timestamp>
  <severity>ERROR|WARN|FATAL</severity>
  <service>service name</service>
  <message>error message</message>
  <root_cause>category</root_cause>
  <suggested_fix>actionable fix</suggested_fix>
</analysis>
</output_format>

Prompt Evaluation Framework

class PromptEvaluator:
    def __init__(self, test_cases: list[dict]):
        self.test_cases = test_cases  # [{"input": ..., "expected": ..., "criteria": ...}]

    async def evaluate(self, prompt_template: str) -> dict:
        results = []
        for case in self.test_cases:
            prompt = prompt_template.format(**case["input"])
            output = await llm.generate(prompt)
            score = self._score(output, case["expected"], case.get("criteria", {}))
            results.append({"input": case["input"], "output": output, "score": score})

        return {
            "avg_score": sum(r["score"] for r in results) / len(results),
            "pass_rate": sum(1 for r in results if r["score"] >= 0.8) / len(results),
            "failures": [r for r in results if r["score"] < 0.8],
        }

    def _score(self, output: str, expected: str, criteria: dict) -> float:
        scores = []
        if "contains" in criteria:
            scores.append(1.0 if criteria["contains"] in output else 0.0)
        if "format" in criteria:
            scores.append(1.0 if self._check_format(output, criteria["format"]) else 0.0)
        if "max_length" in criteria:
            scores.append(1.0 if len(output) <= criteria["max_length"] else 0.0)
        return sum(scores) / len(scores) if scores else 0.5

Checklist

  • [ ] System prompt defines role, task, rules, and output format
  • [ ] Few-shot examples cover edge cases (not just happy path)
  • [ ] Chain-of-thought used for reasoning-heavy tasks
  • [ ] Structured output enforced via JSON mode or XML tags
  • [ ] Prompts tested with evaluation suite (10+ test cases)
  • [ ] Temperature set appropriately (0 for deterministic, 0.7+ for creative)
  • [ ] Prompt versioned and tracked alongside code
  • [ ] Negative examples included ("Do NOT do X")

Anti-Patterns

  • Vague instructions without concrete examples
  • Asking for multiple unrelated tasks in one prompt
  • Not specifying output format (getting unparseable responses)
  • Using temperature=0 for tasks needing diversity
  • Prompt injection vulnerable (no input sanitization)
  • Testing with only 1-2 examples (not statistically meaningful)
  • Hardcoding prompts in application code (not configurable)
  • Ignoring token limits (prompt + expected output exceeds context)

How to use it

Copy the folder

Take vibeeval/prompt-engineering from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

The agent identifies a skill by the name field in its header. Two skills with the same name cannot sit side by side — one of them will be ignored.