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Prompt engineering

As explained in Building Reliable AI Systems

The deliberate design of instructions and context to guide a language model's behavior and outputs.

A customer-support chatbot can sound confident while inventing an answer. Prompt engineering is the iterative design, testing, and refinement of the instructions, context, and examples supplied to a language model. It is a fast first step toward more reliable responses, but a well-phrased prompt cannot supply facts the system does not have. section 2.0 section 5.1.1

Choose prompt techniques according to the failure you need to address:

  • Specify the task and expected behavior clearly. In production, define tone, specificity, response length, and what to do when the request exceeds the assistant’s capabilities; vague instructions leave room for inconsistent answers. section 10.5.2
  • Add a few examples when a task format or unfamiliar concept needs demonstration. For complex problems, demonstrate intermediate reasoning steps; self-consistency instead generates multiple answers and cross-checks them. section 2.9
  • Tune generation settings alongside the prompt. Temperature and top-p affect variability, while length limits and stop sequences control where a response ends. More predictable output is not, by itself, proof of factual accuracy. section 2.9 section 2.0

Test the cheapest intervention first

If an e-commerce chatbot sounds robotic, add a system instruction to respond professionally and warmly, then test it against real customer queries. For a broader quality problem, try an improved prompt on ten real examples; if eight meet the quality bar, prompting may be sufficient. If the bot needs changing inventory figures, supply fresh data through retrieval instead. If stable requirements such as a specialized format remain inconsistent, consider fine-tuning. section 5.1.1

Treat a deployed prompt as a quality contract, not a one-off instruction. Test it across diverse inputs and provide an escalation path for requests the model cannot handle. Version prompt changes so an adjustment can be selected and compared with an earlier behavior. section 10.5.2

PROMPT_VERSIONS = {                                        #1
    "customer_support_v1.0": "You are a helpful customer support agent...",
    "customer_support_v1.1": "You are a helpful customer support agent.
        Always be empathetic...",
    "customer_support_v2.0": "You are a customer support agent for AcmeSoft..."
}

def get_prompt(version="latest"):                          #2
    if version == "latest":
        version = max(PROMPT_VERSIONS.keys())
    return PROMPT_VERSIONS[version]

A Python prompt registry shows how named versions and a selection function can make prompt changes explicit in an application. section 10.5.2

Use feedback to decide what to revise. Group complaints by accuracy, length, tone, missing information, and escalation rather than reacting to isolated reports. Repeated tone complaints suggest a prompt adjustment; repeated missing-information reports suggest a knowledge-base gap. Track whether changes help users complete tasks, not just whether responses sound better. section 10.4.3

How Building Reliable AI Systems covers it

How deep it goes
Develops an iterative workflow with examples, reasoning prompts, generation settings, testing, and production versioning; defers fresh factual grounding to retrieval.
Examples
Uses an e-commerce chatbot’s tone, changing inventory, a legal assistant’s vague instructions, and a Python prompt-version registry.
What it assumes
Assumes familiarity with LLM applications while defining prompt engineering and explaining its core techniques and generation controls.
What you can do after
Practice/perform prompt revision against real queries, then choose retrieval or fine-tuning when prompts do not meet the quality bar.
How it connects
Connects prompt engineering to hallucinations, few-shot prompting, chain-of-thought prompting, retrieval-augmented generation, fine-tuning, and monitoring.

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Related concepts

This explainer was generated by Manning's knowledge graph from the text of Building Reliable AI Systems. The section links point to the parts of the book it draws on.