Agent Base Definition: Why It Is Not a Prompt
When many people first start building Agents, the most natural reaction is: if we make the system prompt longer, write the rules in more detail, will the model then "work like an Agent"?
This intuition is reasonable. After all, in chat products, the prompt seems to decide everything: tone, role, boundaries, and output format can all be shaped by a few paragraphs.
But as soon as a task changes from "answer one question" to "keep working until something is done," prompt is no longer enough.
Suppose we want to build a small CLI assistant:
