Most project overruns begin before the first line of code: the team builds what it understood, not what the business needed. A clear brief is the cheapest way to prevent this, and it does not require technical knowledge.
Start with the goal
Describe why the project exists in business terms: more requests from the website, less manual work in the office, launching a new service, replacing an outdated system. Add how you will know it worked - for example, the number of requests per month or the time spent on a process. A goal helps the team make hundreds of small decisions in the right direction.
Describe the users
Who will use the product: customers, employees, partners, administrators? What do they need to do, and in what situations - on a phone on the go, at a desk all day, once a year? Even a short paragraph about each group is more useful than a list of features.
List the key scenarios
Write the main actions as simple stories: "A customer chooses a service, picks a time, pays and receives a confirmation." Five to ten such stories cover the core of most projects. They are easy to discuss, to estimate and to check at the end.
Be honest about constraints
Budget range, deadline, existing systems that must be connected, legal requirements, languages, who will manage content after launch. Constraints are not a weakness of the brief - they are what allow the team to propose a realistic solution instead of an ideal one.
Set priorities
Mark what must be in the first version and what can wait. A launch with the essential scenarios working well is almost always better than a late launch with everything half-finished.
What you can leave out
You do not need to choose technologies, draw every screen or describe the database. That is the team’s job. Examples of websites or products you like - and what exactly you like about them - are often more valuable than detailed drawings.
The short version
A useful brief answers five questions: why, for whom, what users must be able to do, within which limits, and what comes first. Two or three pages are usually enough to save weeks of rework.