A mobile app brief is typically written by a person or company who is looking to develop a mobile app. The goal of the brief is to provide an app developer with a snapshot of your business, your objectives, the requirements and your overall budget and timeline.
A structured and well-defined application brief will save you time, money and hassle down the line, and help you zone in on the right partner for building your app. Here's what you should include in your application brief:
A summary of your business, your products and/or services. Who are your customers? Who are some of the main competitors? This intro gives the developer valuable context about who you are and what you do.
What is the problem your mobile app should solve? Try to define the problem from the perspective of the user. In other words - focus on the problem, not the solution which you may be envisioning already.
What are you trying to achieve by making an app? There must be a clear business goal or outcome you are seeking. Should the app generate sales? promote your brand? increase customer loyalty? generate new leads? improve a business process? There should be one main objective, with possibly a secondary objective. The objective will guide everyone along the way and be used to measure the performance of the app after it is released.
Define the target audience for the app, and focus on specific personas. Who will download and use this app, and why? Be as specific as possible in identifying the target persona including all the relevant details: region, language, age, profession, socio-economic status. What is the biggest problem that the app aims to solve for this target persona? How does the target persona solve this problem now?
List your high-level requirements along with priorities. MoSCoW is a good prioritization methodology you should consider. Separate requirements to business (your business model / monetisation, branding, etc.) functional (what should it do, and how - detail the user journeys), and technical (which platforms or existing services it should integrate with). Define your requirements as user stories. You may not have all of the above at the outset, and you may require your app developer to formalize these requirements for you. If you know of any examples (existing apps) that meet similar requirements, now is the time to mention them.
This is a crucial section which is often missed. Thinking about your budget and anchoring a number, or even a range, may help you zone in on the right partner much faster. If you have any expectation regarding cost, or any budget that has been pre-allocated for this project which cannot be exceeded, mention it. If your budget is too low in order to achieve the result you want, your app delveloper should explain why this is the case, and you may consider re-prioritizing your requirements or moving stuff to a later release. If your budget is too high... well no budget is too high, really.
Do you have a hard deadline to meet? Are there any dependencies that the app developer should be aware of, such as an existing backend or API, designs, existing code base, etc.? Are you looking to have the app ready for a specific event or campaign launch?