How to Write Better Requirements: Expert Tips and Best Practices

Common weaknesses in requirements

When reviewing requirement specifications in real-world projects, you often see the same recurring issues.

One of the most common weaknesses is unclear wording. Requirements are often written in such a complicated or “clunky” way that people first need to figure out what the actual requirement even is. This makes it especially difficult for third parties to clearly and accurately understand what is actually needed.

Closely related to this is ambiguity or a lack of precision. Descriptions are often intentionally or unintentionally kept vague. Conditional phrasing and terms such as “desirable,” “fast,” “suitable,” or “flexible” leave too much room for interpretation and inevitably create different expectations because no one knows exactly what these terms mean. This often results in repeated clarification meetings or incorrect assumptions that later require costly corrections.

Another issue is incorrect or unnecessary requirements. This includes requirements that stakeholders do not actually want, as well as “nice-to-have” requirements that do not contribute to the actual goals of the product and unnecessarily increase development effort. Equally problematic are illegal or non-compliant requirements that violate applicable standards or legal regulations and may prevent future product certification or approval.

Requirements are also frequently incomplete. This means essential information is missing, such as specific conditions or the classic who/what/when/where/how details, forcing engineers to make assumptions that often miss the actual business need.

Finally, requirements are often written in a way that is too restrictive. They unnecessarily predetermine design decisions and limit the solution space, which can result in feasibility challenges or significant additional costs.

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Weaknesses in a set of requirements

Beyond individual requirements, the overall set of requirements can also have weaknesses.

Common examples include unclear structure that makes maintenance and further development difficult, as well as duplicates and contradictions that create uncertainty. In many cases, the overall set is incomplete (meaning important requirements are entirely missing), contains missing or incorrect links (making impact analysis difficult when changes occur), or uses inconsistent terminology and writing styles, making it harder to create a consistent overall picture.

These aspects are critical to overall quality but are intentionally not explored in depth here. This article focuses on the characteristics of strong individual requirements—because that is often where the biggest opportunity for improvement lies.

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Characteristics of good requirements and practical best practices

The following characteristics directly address the weaknesses described above. For each characteristic, you’ll find practical writing guidelines that have proven effective in real-world projects.

Clarity of requirements

A good requirement should be easy to understand immediately. If multiple people interpret the same requirement differently, it is not written clearly enough. Clarity is the foundation for everything else; without it, misunderstandings are inevitable.

Best Practices:

• Use short, simple sentences without complex sentence structures. The longer and more complicated a requirement becomes, the more likely others are to misunderstand it.
• Always separate the actual requirement text from additional information such as sources, rationale, or links to other requirements. These details are important—but they do not belong in the requirement description itself.
• Write requirements atomically, meaning each requirement should describe only one function or characteristic. Avoid combining multiple expectations into a single requirement.
• If a requirement contains many details, use bullet points instead of long, comma-separated sentences.
• Avoid abbreviations and technical jargon whenever possible—or define them clearly in a glossary.
• Always ensure proper grammar and spelling.

Precision of requirements

Precise requirements reduce room for interpretation. The goal is for every requirement to be understood as clearly as possible and leave no room for different interpretations. Vague wording almost always leads to questions or implementation errors.

Best Practices:

• Always use active language that clearly states what the system (or subsystem) must do. For example: “The system shall process…” Avoid passive constructions such as “…will be processed.”
• Use words such as “shall” or “must” to make it clear that something is a requirement rather than a description of the current state. Avoid present tense (“The system processes…”), future tense (“The system will process…”), or weak phrasing such as “should,” “could,” or “might.”
• Avoid weak terms such as “as much as possible,” “suitable,” “similar,” or “comparable.”
• Avoid relative clauses and unnecessary subordinate clauses. Explicitly name subjects and objects (“the system,” “the data,” etc.) instead of using vague references such as “it” or “these.”
• Replace vague adjectives such as “fast,” “secure,” “reliable,” or “easy” with measurable criteria (e.g., time limits, quantities, thresholds).
• Use precise nouns instead of generic terms—for example, don’t write “documents” if you can specify exactly which documents are meant.

Correctness of requirements

A requirement is only valuable if it is factually correct. This means it must not only be technically accurate but also aligned, necessary, and compliant with higher-level requirements or regulations. Incorrect requirements directly lead to incorrect implementation outcomes.

Best Practices:

• Only document requirements that have been aligned and approved. If approval is still pending, clearly mark that status (note: this information should not be part of the requirement text itself).
• Ensure every requirement can be traced back to a stakeholder goal (note: the traceability link itself should not appear in the requirement description).
• Verify compliance with laws, standards, and regulatory requirements.
• Involve subject matter experts in validation.
• Keep requirements up to date and regularly review them for continued relevance.

Completeness of requirements

Every individual requirement must be complete on its own. It should not leave open questions that need to be answered through assumptions. Completeness means clarity about all necessary aspects.

Best Practices:

• Avoid excessive nominalization and use clear verb-based language. For example, instead of saying that the system should provide an export feature, specify that the system shall export X from A to B in format C.
• Make sure requirements are fully specified (who, what, when, under which conditions, etc.).
• Consider all relevant scenarios, including exceptions and edge cases (note: in most cases, each scenario should become its own requirement or sub-requirement).

Avoiding over-restriction in requirements

Requirements should not unnecessarily limit the solution space. They should describe what needs to be achieved, not how it should be implemented. Locking in specific solutions too early often leads to suboptimal outcomes.

Best Practices:

• Avoid specific technical constraints (e.g., programming languages or material specifications) unless they are absolutely necessary.
• Describe requirements from a black-box perspective. Assume you do not know how the product works internally and focus only on externally observable behavior.
• Do not embed tasks for developers or suppliers directly into requirements. These action items should be documented separately.

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Conclusion

Many problems in requirements management can be traced back to recurring weaknesses: unclear wording, lack of precision, incomplete content, or unnecessary restrictions.

The five characteristics discussed here - clarity, precision, correctness, completeness, and avoiding unnecessary restrictions - provide a solid foundation for systematically preventing these issues.

Of course, additional quality criteria and methods exist in the literature. However, the best practices outlined here are based on many years of real-world project experience and do not conflict with established standards.

If you consistently apply these principles, you’ll quickly notice the difference: requirements become clearer, alignment becomes more efficient, and implementation becomes far more robust.