Spec

A spec is the written statement of what the work should produce: the behaviour, the constraints, the edge cases, and how success will be checked. For an agent it is the most important input to a task, because a coding agent will happily build the wrong thing with great confidence. The spec converts your intent, which lives in your head, into context the agent can actually use.

Without one, the agent fills every gap with its own guess. Ambiguity you would have caught in a five-minute conversation becomes a merged implementation of the wrong idea, and in an AFK run there is nobody to ask. A missing spec also makes review harder: you cannot tell whether the result is right when nobody wrote down what right means.

Write specs at the level of behaviour, not code. Say what happens when the input is empty, what the API returns, what must not change. Include the checks that will prove it: tests to add, commands that must pass. Many people build the spec through grilling, letting the agent interrogate the idea before anything is written. Then commit the spec so it survives clearing and doubles as a handoff artifact.