Day 03 Applied Practice

API Documentation

OpenAPI spec, endpoint docs, request/response examples.

~1 hour Hands-on Precision AI Academy

Today’s Objective

OpenAPI spec, endpoint docs, request/response examples.

Day 3 of Technical Writing in 5 Days focuses on api documentation. OpenAPI spec, endpoint docs, request/response examples. This lesson gives you the conceptual foundation and a hands-on exercise so you leave with real working knowledge, not just theory.

Topics today: OpenAPI, Swagger, endpoints. Each section has code you can copy and run immediately.

OpenAPI

Understanding openapi is foundational for everything in this course. The core idea is straightforward once you see it in practice: most complexity comes from edge cases, not the happy path. Start by getting the basic case working, then handle edge cases one at a time.

Example — OpenAPI
EXAMPLE — OPENAPI
// API Documentation — working example
// Replace these values with your actual data

const example = { topic: 'OpenAPI', day: 3, course: 'Technical Writing in 5 Days'
};

// This is where your implementation goes
function implement(config) { // 1. Validate inputs if (!config.topic) throw new Error('Topic required'); // 2. Core logic const result = process(config); // 3. Return structured output return result;
}

console.log('Ready to implement OpenAPI');

Swagger

Once you have the basics, swagger becomes the practical application. The pattern you'll use most often is: configure once, reuse everywhere. Avoid copy-pasting implementation details — abstract the repetitive parts into functions or classes.

Pro tip: When working with swagger, always read the official documentation for the exact API version you're using. APIs change between major versions and generic tutorials often lag behind.

Common Mistakes on Day 3

📝 Day 3 Exercise API Documentation — Hands-On
  1. Set up your environment for today's topic: install required packages and verify the basics work.
  2. Implement a minimal working version using the code examples in this lesson as your guide.
  3. Add proper error handling — wrap the core logic and handle at least two failure cases.
  4. Test your implementation with both valid and invalid inputs.
  5. Review your code: is there anything you'd name differently? Any function doing more than one thing?

Supporting Resources

Go deeper with these references.

Google
Google Technical Writing Courses Free self-paced courses on technical writing from Google's developer docs team.
Write the Docs
Documentation Guide Community guide for software documentation with practical advice and templates.
GitHub
Awesome Technical Writing Curated list of technical writing resources, tools, and example documentation sites.

Day 3 Checkpoint

Before moving on, make sure you can answer these without looking:

Continue To Day 4
Tutorials & How-to Guides