Spec
A written description of what an app should do and how it should look, detailed enough to build from.
What it is
A spec (specification) is the plan: who uses the app, what they can do, what data it keeps, what each screen shows, and the rules and edge cases. It's the single most useful thing you can give a coding agent.
A good spec is concrete. It makes decisions instead of listing options, names the things involved ("a toast", "a drawer", "a manager role"), and says what happens when things go wrong.
It doesn't need to be long or technical. A page of clear, specific prose beats ten pages of vague wishes.
How to ask for it
“Build me an app for my cleaning business.”
“Spec: a booking app for a home cleaning business. Customers pick a service, date, and 2-hour slot, and pay a deposit. Staff see a daily schedule. Admins manage services and prices. Customers get an email confirmation and a reminder the day before.”
"An app for my business" forces the builder to invent everything; a spec names the users, actions, and rules.
You've seen this in
- PProduct requirement documents at tech companies
- DDesign briefs for agencies
- TThe description you give a coding agent before it builds