3-2 Writing Better Technical Design Documents with Cursor

In Software Development is More Than Writing, we established that software development involves much more than coding. Now you face one of the most challenging non-coding tasks: writing a technical design document.

Say you want to write a design doc for your messaging system's new multimedia feature. It's likely that you would stare at a blank markdown file, trying to figure out how to extend your text-only chat system to support images and videos.

You need to consider storage solutions, performance implications, security measures, and scalability concerns. The complexity feels overwhelming, and you haven't even started thinking about how to communicate these technical decisions clearly to your team.

This scenario illustrates why technical design documents remain one of the most difficult aspects of software development. They require both deep technical analysis and clear communication skills. Cursor transforms this challenge by helping you brainstorm design alternatives, get feedback on existing proposals, and create visual diagrams that make complex concepts accessible.

Design Documents in Code Repositories

A growing industry trend places technical design documents directly in code repositories rather than external documentation systems. GitHub's CEO mentioned in an interview that nearly all of GitHub's documentation now lives on the GitHub platform itself.

This approach provides several advantages. Git's built-in version control makes managing document versions straightforward compared to external documentation systems. More importantly, storing design documents alongside code creates direct connections between design decisions and their implementations. When someone questions a code segment, they can immediately find the relevant design document in the same repository.

With AI tools like Cursor, keeping design documents in your codebase becomes even more valuable. You can work on documentation while leveraging the full context of your project structure and existing code patterns.

Scenario 1: Brainstorming Design Alternatives

Cursor excels at helping you explore different technical approaches when facing complex design decisions. Consider extending a chat system that currently supports only text messages to handle multimedia content like images and videos.

Start by providing your existing design document as context using @file to reference the current technical specification. Then engage Cursor in technical brainstorming by enabling "Thinking" mode for reasoning models, which perform better on complex analytical tasks like system design.

Your prompt might look like: "In this chat system design document, we currently only support text messages, but our PM wants to add multimedia messaging functionality for images and videos. Based on the existing technical design, please provide several different technical design approaches to support multimedia messaging."

With reasoning models enabled, Cursor will first think through the problem systematically, then provide multiple technical approaches with detailed trade-offs. It will consider factors like file storage efficiency, performance optimization, and security implications—all critical concerns when handling multimedia files that are significantly larger than text messages.

Use these suggestions as inspiration rather than final solutions. Cursor provides valuable starting points for your thinking, but you need to evaluate each approach's feasibility within your specific technical constraints and business requirements.

Scenario 2: Getting Feedback on Existing Designs

Beyond brainstorming new approaches, Cursor can analyze existing design decisions and suggest improvements. Suppose your chat system design includes group messaging functionality, but the current architecture has scalability limitations that cause problems when group sizes increase.

Select the relevant text section from your design document and use Command + I to add it to Cursor's chat interface. Then ask for specific feedback: "The current group chat design has scalability limitations and struggles to support larger group sizes. Please suggest different design perspectives to overcome these limitations."

Unlike the brainstorming scenario, this approach focuses on improving existing architecture rather than creating something entirely new. Cursor will analyze your current design and suggest specific modifications to address scalability concerns, such as implementing message queuing systems, database sharding strategies, or connection pooling techniques.

Again, treat these suggestions as brainstorming input rather than definitive solutions. Your technical judgment remains essential for evaluating the practicality and appropriateness of each recommendation.

Scenario 3: Creating Visual Diagrams

Technical design documents filled with dense text can be difficult to read and understand. Your chat system design document might contain comprehensive technical details, but without visual elements, team members struggle to grasp complex concepts quickly.

Cursor can generate diagrams that significantly improve document readability. For example, if your document contains a text description of one-to-one messaging flow, you can select that text and ask Cursor: "This text-only content is hard to read. Please add an ASCII diagram to help explain it."

While ASCII diagrams provide basic visualization, Mermaid diagrams offer superior clarity and professional appearance. You can request: "Please generate a Mermaid diagram based on this content." For messaging flows, Cursor will create a sequence diagram with proper Mermaid syntax that you can paste into the Mermaid online editor to generate a professional-looking diagram.

Adding these diagrams to your design documents dramatically improves readability and helps team members understand complex technical concepts at a glance. The combination of detailed text explanations and clear visual representations makes your documentation both comprehensive and accessible.

Transforming Documentation Quality

These three scenarios demonstrate how Cursor transforms technical design document creation from a solitary struggle into a collaborative process. You can brainstorm design alternatives, get analytical feedback on existing proposals, and generate visual aids that make complex concepts understandable.

The key to success lies in maintaining your role as the technical decision-maker while leveraging Cursor's ability to generate ideas, analyze trade-offs, and create visual representations. This approach produces more thorough, well-analyzed, and readable design documents that genuinely help your team understand and implement complex technical systems.

When you next face the challenge of writing a technical design document, remember that Cursor can assist with both the analytical thinking and the communication aspects, letting you focus on making sound technical decisions based on comprehensive analysis and clear presentation.

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