Prompt Engineering Essentials
Master the art of crafting effective prompts to unlock the full potential of AI agents
Understanding Prompt Engineering
Prompt engineering is the art and science of crafting inputs to AI models to achieve desired outputs. It's one of the most critical skills for AI agent development, as the quality of your prompts directly determines the effectiveness of your agents.
Key Insight
Prompt engineering is to AI what programming is to computers—a way to provide instructions that produce specific behaviours and outputs.
Why Prompt Engineering Matters
The same AI model can produce dramatically different results based solely on how you structure your prompts. Effective prompt engineering can:
- Improve Output Quality: Generate more accurate, relevant, and useful responses
- Enhance Reliability: Reduce hallucinations and inconsistencies
- Increase Efficiency: Accomplish tasks with fewer interactions and tokens
- Enable Complex Tasks: Break down complex problems into manageable steps
- Control Behaviour: Shape the model's persona, tone, and response style
The Evolution of Prompt Engineering
| Era | Approach | Example |
|---|---|---|
| Basic Prompting | Simple questions or instructions | "What is machine learning?" |
| Structured Prompting | Formatted instructions with context | "Explain machine learning in simple terms. Include examples." |
| Few-Shot Learning | Including examples of desired outputs | "Q: What is AI? A: Artificial Intelligence is... Now, Q: What is machine learning? A:" |
| Chain-of-Thought | Encouraging step-by-step reasoning | "Think step by step to solve this problem..." |
| Advanced Techniques | Specialised patterns for specific tasks | ReAct, Tree-of-Thought, Self-Consistency, etc. |
| Agent Prompting | Prompts that enable autonomous behaviour | System messages defining roles, capabilities, and workflows |
Core Prompt Engineering Principles
Regardless of the specific technique, these fundamental principles apply to all effective prompt engineering:
1. Clarity
Clear prompts produce clear outputs. Ambiguity in your prompts leads to unpredictable results.
Clarity Guidelines:
- Be Specific: Clearly state what you want the model to do
- Use Simple Language: Avoid jargon unless necessary
- One Task Per Prompt: Focus on a single objective
- Structured Format: Use headings, bullet points, and sections
Before vs. After Example
Before (Unclear): "Tell me about AI agents."
After (Clear): "Explain what AI agents are, how they work, and provide three examples of their practical applications in business settings. Include a brief explanation of how they differ from simple chatbots."
2. Context
Providing relevant context helps the model understand the scope and background of your request.
Context Guidelines:
- Background Information: Include relevant facts and circumstances
- User Needs: Explain who will use the information and why
- Prior Knowledge: Reference previous interactions when relevant
- Domain Specificity: Clarify the field or domain (e.g., medical, legal, technical)
Before vs. After Example
Before (No Context): "Write code to process data."
After (With Context): "I'm a marketing analyst with basic Python knowledge. Write code to process CSV data containing customer purchase history. The data includes customer ID, purchase date, product ID, and amount. I need to calculate the average purchase value per customer and identify the top 10 customers by total spend."
3. Specificity
Detailed instructions about the desired output format, style, and content lead to more useful results.
Specificity Guidelines:
- Output Format: Specify the desired structure (paragraphs, bullet points, table, etc.)
- Length: Indicate approximate word count or detail level
- Tone and Style: Define the writing style (formal, conversational, technical)
- Content Elements: List specific points or sections to include
Before vs. After Example
Before (Vague): "Write a blog post about AI safety."
After (Specific): "Write a 1000-word blog post about AI safety for a technical audience with some AI background. Structure it with an introduction, 3-4 main sections covering key risks (specifically including alignment problems and misuse), current mitigation approaches, and future research directions. Use a professional but accessible tone, include 2-3 real-world examples, and end with actionable takeaways for AI developers."
4. Iterative Refinement
Prompt engineering is an iterative process that requires testing and refinement to achieve optimal results.
Refinement Process:
- Start Simple: Begin with a basic version of your prompt
- Test: Evaluate the output against your requirements
- Identify Issues: Note specific problems or shortcomings
- Refine: Modify your prompt to address the issues
- Repeat: Continue testing and refining until satisfied
Prompt Iteration Example
Version 1: "Summarise this research paper."
Issue: Summary is too general and misses key findings.
Version 2: "Summarise this research paper, focusing on methodology and key findings."
Issue: Better, but lacks structure and is too verbose.
Version 3: "Create a structured summary of this research paper with these sections: 1) Research Question, 2) Methodology, 3) Key Findings, 4) Limitations. Keep each section concise with bullet points where appropriate."
Result: Well-structured, focused summary highlighting the most important aspects of the paper.
High-ROI Prompt Engineering Techniques
These advanced techniques provide the highest return on investment for AI agent development:
1. Structured Tool Usage
Using structured formats for tool calls ensures consistent and reliable interaction between your AI agent and external tools or APIs.
XML-Style Tool Call Template:
value1
value2
This approach has several advantages:
- Clear delineation between tool calls and regular text
- Explicit parameter naming to avoid confusion
- Nested structure for complex parameters
- Easy parsing with regular expressions or XML parsers
Example Implementation
import re
def extract_tool_calls(text):
"""Extract tool calls from text using regex."""
# Improved regex to handle nested tags (non-greedy match)
pattern = r'<(\w+)>(.*?)\1>'
tool_calls = []
# Find all top-level tool calls
matches = re.finditer(pattern, text, re.DOTALL)
for match in matches:
tool_name = match.group(1)
tool_content = match.group(2).strip()
# Extract parameters within this tool call
params = {}
param_pattern = r'<(\w+)>(.*?)\1>'
param_matches = re.finditer(param_pattern, tool_content, re.DOTALL)
for param_match in param_matches:
param_name = param_match.group(1)
param_value = param_match.group(2).strip()
# Basic handling for potential nested structures (more robust parsing needed for deep nesting)
if '<' in param_value and '>' in param_value:
# Could potentially parse nested structure here if needed
pass # For simplicity, keep as string for now
params[param_name] = param_value
tool_calls.append({
"tool": tool_name,
"params": params
})
return tool_calls
# Example usage
text = """
I'll search for that information.
latest AI research papers 2025
5
Let me analyse these results for you.
"""
tool_calls = extract_tool_calls(text)
print(tool_calls)
2. Plan Mode vs. Act Mode
Separating planning from execution creates more effective and reliable AI agents by ensuring thorough preparation before action.
Two-Mode Agent Approach:
| Mode | Purpose | Characteristics |
|---|---|---|
| Plan Mode | Gather information and create strategy | High reasoning, low creativity (low temp), uses information gathering tools |
| Act Mode | Execute the plan using tools | Instruction following, higher temperature for creative tasks, uses action tools |
Implementation Strategy:
- Agent receives a task
- Enters Plan Mode: Determines steps, identifies needed tools/info
- Agent generates a plan (e.g., list of steps or tool calls)
- Optional: Human reviews or approves the plan
- Enters Act Mode: Executes the plan step-by-step
- Handles errors or deviations by potentially returning to Plan Mode
3. Meta-Prompts (Prompts for Prompts)
Use LLMs to generate or refine prompts for other LLM calls. This allows dynamic adaptation based on context.
Example: Dynamic Summary Prompt Generator
Input: User request ("Summarise this financial report for an executive")
Meta-Prompt: "Generate a detailed prompt for GPT-4 to summarise the provided text. The user is an executive. The summary should be concise, focus on key financial metrics, and highlight potential risks or opportunities."
Output Prompt (Generated): "You are an expert financial analyst. Summarise the following financial report specifically for a busy executive. Focus on: 1) Overall profit/loss trends, 2) Key revenue drivers, 3) Major expense categories, 4) Significant risks or opportunities identified. Keep the summary under 250 words using clear, non-technical language."
4. Self-Correction Prompts
Instruct the LLM to review its own output against specific criteria and correct any errors or deficiencies.
Self-Correction Prompt Template:
[Original Prompt generating initial output]
[Generated Output]
Now, review the generated output based on the following criteria:
- Criterion 1: [Description]
- Criterion 2: [Description]
- Criterion 3: [Description]
Identify any flaws or areas for improvement based on these criteria.
Then, generate a revised version of the output that addresses these issues.
5. Persona-Based Prompting
Assigning a specific persona or role to the LLM in the system message helps focus its knowledge and response style.
Persona Examples:
- "You are an expert Python programmer specializing in data analysis..."
- "You are a helpful customer support agent for a SaaS company..."
- "You are a creative copywriter crafting compelling marketing slogans..."
- "You are a meticulous editor focused on grammar, clarity, and style..."
Structuring Prompts for Agentic Behaviour
Building autonomous AI agents requires prompts that define their goals, capabilities, tools, and workflow.
Key Components of an Agent Prompt
Agent System Message Template:
# Role and Goal
You are [Agent Name], a [Role Description] designed to [Overall Goal].
# Core Capabilities
Your primary capabilities include:
- Capability 1: [Description]
- Capability 2: [Description]
- ...
# Available Tools
You have access to the following tools:
- Tool 1: `` - [Description and parameters]
- Tool 2: `` - [Description and parameters]
- ...
# Workflow / Process
To achieve your goal, follow these steps:
1. Analyze the user request.
2. Determine the necessary information or actions.
3. Select the appropriate tool(s) and parameters.
4. Execute tool calls using the specified XML format `value `.
5. Synthesize the results and formulate a response.
6. If unable to complete the task, explain the issue and ask for clarification.
# Constraints and Guidelines
- Only use the provided tools.
- Think step-by-step before acting.
- Respond concisely and professionally.
- Handle errors gracefully.
- [Other specific rules]
# Current Conversation History
[History inserted here]
# User Request
[User's latest input here]
# Agent Response (Your turn)
Begin your response here. Use tool calls when necessary.
This structured system message provides the LLM with all the context it needs to operate as an autonomous agent within its defined boundaries.
Evaluating Prompt Performance
Systematic evaluation is key to improving prompt effectiveness. Combine qualitative and quantitative methods:
Qualitative Evaluation
- Human Review: Assess outputs for accuracy, relevance, clarity, and tone
- Side-by-Side Comparison: Compare outputs from different prompt versions
- Error Analysis: Categorize common failure modes (hallucinations, vagueness, irrelevance)
Quantitative Evaluation
- Automated Metrics: Use metrics like BLEU, ROUGE (for summarization), or code evaluation tools
- LLM-as-Judge: Use a powerful LLM (like GPT-4) to evaluate outputs against criteria
- A/B Testing: Deploy different prompt versions and measure user satisfaction or task success rates
LLM-as-Judge Example Prompt
You are an impartial evaluator. Evaluate the following AI-generated response based on the user query and specific criteria.
User Query:
[Insert User Query]
AI Response:
[Insert AI Response]
Evaluation Criteria:
1. Accuracy: Is the information factually correct?
2. Relevance: Does the response directly address the user query?
3. Clarity: Is the response easy to understand?
4. Completeness: Does the response cover all aspects of the query?
Instructions:
For each criterion, provide a score from 1 (Poor) to 5 (Excellent) and a brief justification.
Finally, provide an overall quality score from 1 to 5.
Evaluation:
Accuracy Score: [1-5]
Justification:
Relevance Score: [1-5]
Justification:
Clarity Score: [1-5]
Justification:
Completeness Score: [1-5]
Justification:
Overall Quality Score: [1-5]
Overall Justification:
Next Steps: LangChain Basics
Mastering prompt engineering is crucial, but building complex agents often requires frameworks to manage prompts, LLM calls, memory, and tool integration. LangChain is a popular choice for this.
Key Takeaways from This Section:
- Prompt engineering is critical for controlling AI agent behavior and output quality
- Core principles include clarity, context, specificity, and iterative refinement
- High-ROI techniques include structured tool usage, planning vs. acting modes, meta-prompts, self-correction, and personas
- Agent prompts require defining roles, goals, capabilities, tools, and workflows
- Systematic evaluation using both qualitative and quantitative methods is essential for improvement
In the next section, we explore LangChain Basics, providing an introduction to this powerful framework for building sophisticated AI applications and agents.
Continue to LangChain Basics →