We often feel a rush of excitement when a new idea hits. Most of us want to open our code editor and start typing logic immediately. We want to see the project run as soon as possible. However, as a project grows, we often realize that code does not exist in a vacuum.
If you are the only one who knows how the code works, the project will eventually fail. This is especially true in open source where you need other people to help you. Documentation is not just for the people using your software. It is also for the people building it.
The biggest mistake is treating documentation as something you do at the very end. When you write docs last, you are usually tired or rushed. This leads to guides that are missing steps or are already out of date. When a user finds a guide that does not match the code, they will likely stop using your project.
What is Docs-Driven Development?
Docs-Driven Development (DDD) is a simple method. You write your README, tutorials, and API rules before you write any actual code.
In this workflow, the documentation is not a summary of what you finished. Instead, it is a plan for what you are about to create. If you cannot explain how a feature works in simple words, you probably should not be coding it yet. This method forces you to think about the person using the software before you get lost in the technical details.
The 3 Core Pillars of DDD
To understand why this works, we have to look at the three ideas that hold it up:
1. The Documentation is the Spec
In traditional building, you have a blueprint before you lay bricks. In software, your documentation is that blueprint. By writing the API and the "how-to" first, you create a clear set of rules for your code to follow. This prevents "feature creep," which is when a project gets too big and messy because it lacks a clear plan.
2. The "Readme-First" Workflow
DDD turns the traditional development cycle on its head. Instead of coding and then trying to remember what you did, you follow a deliberate sequence:
- —Draft: Write the "How-to-use" guide and define your API signatures.
- —Review: Share these docs with your community or team to see if the logic makes sense to them.
- —Code: Build the logic specifically to satisfy the examples you already wrote.
- —Verify: Ensure the final code and the docs match perfectly.
3. A Single Source of Truth
Projects often fail because different team members have different ideas of how a feature should work. If the documentation is written first and agreed upon, everyone has the same goal. There is no confusion about what the final product should do because the "truth" is already written in the README.
Why docs-driven documentation is important
- —It reduces rework. It is much easier to delete a sentence in a Markdown file than it is to rewrite a complex library because the logic was wrong.
- —It creates "self-service" support. In open source, maintainers spend a lot of time answering the same questions. Good docs answer these questions before they are even asked. This gives you more time to focus on building features.
- —It makes onboarding easy. When a new contributor wants to help, they do not have to read thousands of lines of code to understand your goal. They can read the docs and start contributing immediately.
- —It acts as a test. If a feature is too hard to explain in the docs, it is usually too hard to use. This "explanation test" helps you keep your software simple and clean.
Components of Good Documentation
For a small project, you might only need a README. However, as your product grows, you should add more parts. Not every project needs every component. For example, a simple CSS library might not need a "Cookbook," but it definitely needs a "Reference."
- —The README: Your elevator pitch and quick-start guide. It explains what the project is and how to get it running in under a minute.
- —The Reference: The "dictionary" of your project. This covers every API call, parameter, and configuration option in detail.
- —The Cookbook: These are step-by-step guides for specific tasks. They show how to solve a real problem.
- —The User Guide: A deeper dive into the concepts and philosophy behind the software.
- —The CONTRIBUTING File: This tells people how to set up their local environment, run tests, and submit a Pull Request.
The goal of software is to be used. If people cannot understand how to use your tool, the quality of your code does not matter. Switching to a docs-first mindset might feel slow at first, but it creates a much stronger foundation.
By writing the manual before the code, you ensure that your project is built for people. Start your next project with a README file and see how much clearer your path becomes.