How to Write Your Own AI Commands
You do not need prompt-engineering theory to write a command that works. You need a method: take a task you already do, strip it to its fixed shape, and write four things — role, input, goal, constraints. This guide walks through that method on a real example, and covers the two failure modes that make saved commands feel disappointing.
Start from a task you already do
The best command to write is one that already exists in your week. Do not invent a hypothetical. Pick something you did twice this month, and write down what you typed both times — the overlap between the two versions is the command.
The four parts
- Role — who the model should be. 'You are a technical editor' changes the output more than any other single line.
- Input — where the material comes from, and where the placeholders are.
- Goal — what a great result looks like, in enough detail to be checked.
- Constraints — length, format, tone, and what to avoid.
A worked before-and-after
summarise this/Standup
You are writing a standup update that a manager reads
in fifteen seconds.
Input: <paste yesterday's notes and today's blockers>
Output exactly three lines, one per line below:
Done: <what shipped>
Doing: <what is in progress>
Blocked: <what is stuck, and on whom — or 'nothing'>
Constraints: one sentence per line, no preamble, past tense for Done
Avoid: hedging, filler, anything that would need a follow-up questionThe important move is the fixed output shape. 'Three lines, this exact format' removes the most common source of disappointing output, which is the model giving you a well-written paragraph when you needed something you can paste into a box.
The two failure modes
- Too vague, so the model fills the gap with its own idea of what you wanted. Fix it by naming the audience and the format.
- Too rigid, so every output is identical and useless. Fix it by stating what should vary and what must not.
Storing them
Keep a paste bin for commands you use constantly, and a note for the ones you are still refining. The Markdown editor is a good home for a library, because plain text survives every tool you might move to next.
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