Guidelines for a Comprehensive App Requirements Documentation

With a decade of experience building on-demand web, Android, and iOS apps, MadAppGang knows how important it is to describe your project in detail from the outset. It’s crucial that developers understand exactly what they have to create. So, your first step when building an app is to prepare a product requirements document (PRD) that lists the app’s features, functional and non-functional requirements, and so on. 

At first glance, this task seems to be a bit challenging, especially if you’re new to software development. However, a mobile app requirements document (mobile app PRD) can guide the process and help ensure that the final product meets your requirements. 

To help you outline your idea clearly, in this article we cover the essentials of a comprehensive app requirements document. 

But before we get stuck into the details, let's review some of the basics.

A PRD is a comprehensive overview of your product vision. It should contain a detailed description of the concept, objectives, and scope of your project. The technical part of the document must include characteristics of any features in your application and the corresponding functional requirements.

A rough outline for app requirements documentation.

In a word, you should specify end-product capabilities to the development and testing teams. Most of an app requirements document is text, but graphics such as wireframes and sketches can help illustrate your needs.

A PRD provides the basis for creating the product backlog and organising the whole software development process. As with many things, the devil is in the details, and app development is no different. When a development team is provided with a full PRD, there are fewer miscommunications, less time wasted, and you’re more likely to get the product you want and a smoother development process overall. 

There is a widespread opinion that an app PRD is only good for the ‘Waterfall’ style of management, however, at MadAppGang, we find it very useful even though we follow an Agile methodology. For example, a PRD helps plan the tests at an early stage. 

Software testing life cycle model. Source: Guru99

Creating an exhaustive app PRD is crucial for you, as a business owner, so the development team can deliver a product that completely corresponds to your vision, and in time.

Now, let's move on to creating a document with your business and technical requirements.

First, you should know that there is no one "right" way to write an app requirements document, so it’s entirely up to you how to structure the document. What matters is giving your developers precise information on the final product you expect. 

That said, when composing a PRD, the five-step guide below can help.

Describe your idea and objectives

Describe your vision of the product at the beginning of the document. For example, if you want an app that rates the attractiveness of dog breeds, let your potential developers know that at the beginning of your document. Additionally, you can say a few words about the main features and functionality you require.

Try to explain in a few sentences what you want the app to do and present its core objectives. A tight, brief introduction clearly sets out the app’s key concept and what you need from the developers.

Conduct market research

If you want your product to be successful and profitable, robust market research is essential. 

Identify the needs of your target audience and think about how your app can satisfy these. Researching potential users’ ages, locations, occupations, and interests helps you create workable user personas. In turn, these user personas offer a better understanding of the future app’s functional requirements. For instance, if your app-to-be is the world's largest knitting pattern repository, you may discover that your target user will value X feature while Y feature is of less importance.

In this part of the document, you can also add information about the niche you intend to occupy and your closest competitors, including the platform, the approximate number of users, and any other helpful details.

Choose features

After researching the target audience, you’ll have a more explicit picture of the user's expectations. From there, you can start planning the features required to meet the user's needs. 

The best solution for the initial version of your app is to offer a simple and intuitive user experience with few key features. Such an approach is essential when building a minimum viable product (MVP). In this case, you need to be very selective with the features you choose. 

To validate and prioritise features, try the MoSCoW method. Divide features into four "have" categories: must, should, could, won’t. This analysis separates features directly related to business goals from others that are inessential and can be postponed until later iterations of the app.

With the finalised list of features, developers can determine the integrations, APIs, and third-party elements needed.

Prepare functional specifications

Functional requirements provide an exhaustive description of the functions and features of your application. They also explain how the app should perform and respond to user requests. Properly composed functional requirements clarify exactly how the app’s features solve user problems. 

This part of the document must also encompass the mobile app’s technical specifications, such as the platform for launching the app, development tools, description of the app’s interaction mechanism, collaboration with the server, protocols, and data. If you are unable to complete this section yourself, it’s not a big deal as your developers can assist you with this matter.

Apart from this, your functional requirements section may include information on the project’s scope, risks and assumptions and so on. 

Provide wireframes

Sketches and wireframes of your app’s screens give a visual representation of the requirements and make things clear. Wireframes help developers understand how your future app will work, and show the relationship between different features and functionalities. 

You can ask professionals to draw the screen blueprints or do it yourself. You don’t need to be a graphic designer and there are plenty of tools for creating fast and simple sketches. Technologies like Axure RP, Balsamiq, Figma, Sketch can help you make visual representations of your app’s navigation and structure.

Unlike functional requirements that define what the system does, non-functional requirements specify how the system does it. They describe the system's operational capabilities and provide guidelines on how to build the app correctly.

Non-functional requirements example. Source: ResearchGate

Here are some of the main non-functional requirements you should consider:

• Performance: Performance is measured by response time: the faster the system returns results, the better the performance.

• Scalability: This is how well your app handles high workloads and increased user data (stored data, caches).

• Responsiveness: The app should respond to the user’s input or external interrupt and return to the same state. 

• Usability: This criterion defines the quality of the user experience (UX). Users should be able to understand the app’s functions without guidelines or other assistance.

• Reliability: A probability percentage of an app working without failure and delivering expected results for a given time under certain conditions.

• Security: All app data (especially user contacts, payment methods, and such) must be secured and encrypted to protect against malware or unauthorized access.

When including non-functional requirements in your mobile app development requirements document, make sure they are measurable, testable, and correlate with your business objectives.

We’ve already spoken about the importance of a mobile app requirements document and mentioned the essential information it should include. But before you start writing one, here are some helpful tips on creating an exhaustive and reliable PRD.

Make the document comprehensive and clear

Keep in mind that besides the development team and yourself, your requirements document might be read by other people, for example, investors. Therefore, try not to overload it with niche technical terms and keep the language easy to understand.

Ensure each requirement is testable

Writing a requirement with a test scenario in your head is beneficial for you and your developers. It gives your designers and test engineers a clear picture and thorough understanding of what exactly needs to be done. Ensure each requirement is clear, measurable, and the specification is verifiable.

Write in an implementation-neutral manner

By writing your document in an implementation-neutral manner, you won't have to write about the design in detail. If you modify implementations in the future, you won't have to rewrite the requirements from scratch. 

Finalise the requirements document with team members

After you’ve compiled your app PRD, evaluate it with your product development team. Engaging designers, developers, and quality assurance engineers in the process increases the chances that the specs will comply with your needs.

That’s pretty much it. If you consider all the above points and implement them in practice, you’re well on your way to a flawless product requirement document. 

However, if things are still unclear, or you’re feeling overwhelmed, an app development requirements template could be just the ticket.

A generic PRD template isn’t a universal solution because mobile apps differ significantly in both concept and complexity. 

Instead, browse a variety of mobile app requirements templates and use the most suitable one as a basis for your document. You can edit the template by adding required details or removing irrelevant information. As a result, you'll get a PRD template that fits the specifics of your project.

It’s hard to underestimate the significance of an app requirements document in a project. Well-written technical specifications serve as a foundation for a successful product that gets the development process off to a great start.