Prompt engineering has a reputation for being a bag of tricks, but the teams that get consistent results treat prompts the way they treat code: structured, versioned, and tested. A prompt is a specification for behavior, and vague specifications produce vague software.
Structure beats cleverness
The most reliable prompts follow a consistent shape: a role that sets context, explicit instructions, the input data clearly delimited, and a description of the output format. Models respond strongly to structure, so separating instructions from data with headings or XML-style tags prevents the model from confusing the two.
Show, do not just tell
Few-shot examples remain one of the highest-leverage techniques available. Two or three worked examples of input and desired output will usually outperform a paragraph of abstract instructions. Choose examples that cover your edge cases, not just the happy path.
- Pin the output format with a literal example, especially for JSON.
- Cover at least one tricky case, such as missing data or ambiguous input.
- Keep examples short so they do not crowd out the real input.
Treat prompts like code
Store prompts in version control, not in a dashboard textbox someone edits on a Friday afternoon. Build a small evaluation set of representative inputs with expected outputs, and run it whenever the prompt or the underlying model changes. Model upgrades routinely shift behavior, and an eval suite is the only way to catch regressions before your users do.
Finally, resist the urge to fix every failure by appending another rule to the prompt. Long prompts full of contradictory patches degrade. When a prompt stops being legible, refactor it the same way you would refactor a function that grew too long.