What Is Prompt Engineering? A Practical Guide to Context Engineering and KV Cache

Prompt engineering started as a narrow craft and then grew into a much bigger idea. At first, it just meant learning how to write better instructions so a model would give better answers. That is still part of the job. But once people started building real AI agents, the question got bigger. It was no longer just about the wording of the prompt. It became about what context the model sees, what tools it can use, what history it should remember, and how to keep all of that stable enough to run…