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What is prompt engineering?

Prompt engineering is the deliberate design and testing of the instructions, context, examples, output format, and constraints given to an AI model for a specific job.

For teams trying to make AI work repeatably instead of relying on clever one-off prompts. · Reviewed 2026-09-29

A prompt is not just a question

For a useful workflow, the prompt usually needs the task, the audience, the available evidence, the constraints, and the shape of the desired answer. “Write a post about our product” leaves too much hidden. “Turn these approved product facts into three LinkedIn drafts for operations leaders; do not invent metrics” gives the model a job it can follow.

The parts worth designing

  • Instruction: what the model should do.
  • Context: the facts or source material it may use.
  • Constraints: what it must not invent or change.
  • Output contract: headings, fields, JSON, table, or length.
  • Examples: a good and bad result when the distinction is hard.
  • Evaluation: how a human decides whether the result is acceptable.

What prompt engineering cannot do

A better prompt cannot make missing facts current, turn a weak source into evidence, or remove the need for review in a high-risk workflow. If the problem is missing knowledge, use retrieval or a tool. If the problem is unstable requirements, fix the task definition first.

A useful test

Run the prompt against several ordinary examples and at least one awkward case. If the result only works when you keep adding exceptions, the workflow may need a better input contract or a different system design.

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