Why I'm All In for Spec-First Development

Why I'm All In for Spec-First Development

Written by

By Ranjgith

Published on

Jul 21, 2025

3 min read

What’s the Spec-First Buzz All About?

Spec-First Development is like designing the house before you bring in the bricks. It means clearly defining what you want your code to do before writing the first line. Instead of “let’s start coding and see where it goes,” you write down a detailed plan — your blueprint — and follow it.

It flips the usual habit — write code first, document later — on its head. In fact, with a good spec, the documentation practically writes itself.

Why Bother With Specs First?

Yes, it might seem like more work initially. But trust me, it saves you from a ton of “uh-oh” moments later.

Here’s why I’m a big fan:

  • Clarity is Power 🧭: Everyone knows what they’re building.

  • Bugs? Catch ’em Early 🐛: Spot flaws before they become headaches.

  • Everyone on the Same Page 📖: From devs to testers to product folks.

  • AI Needs Guidance Too 🤖: Tools like Copilot shine when the prompt (spec) is crisp.

  • Bonus: Your specs double as documentation!

It Plays Nicely with Modern Workflows 🚀

Still Agile? Still sprinting? You’re not alone. Spec-first doesn’t get in the way — it amplifies your workflow:

  • Agile & BDD: Treat specs like user stories or behavior definitions.

  • CI/CD: Use specs to autogenerate tests, mocks, and even validation.

  • API-First: OpenAPI specs before writing backend logic = chef’s kiss.

  • Iterative Friendly: Specs evolve just like your code.

Where AI Really Starts to Shine 🌟

Spec-first + AI = magic combo.

GitHub Copilot

If you say:

# Function to filter tasks by a keyword (case-insensitive) 
def filter_tasks(tasks, keyword):

Copilot jumps in with:

return [t for t in tasks if keyword.lower() in t.title.lower() or keyword.lower() in t.description.lower()]

🎯 Precise, quick, and surprisingly smart when it’s got a solid spec.

Windsurf by Codeium

Think of this as the pro-surfer version of AI IDEs. With “Cascade” mode, it can edit multiple files based on one spec, test things, manage workflows — all from a simple intent.

Quick Example Walkthrough

Spec: "A function that takes a list of tasks and a keyword and returns only the ones that include the keyword in the title or description (case-insensitive)."

You write:

def filter_tasks(tasks, keyword):
    # ... 

AI writes:

return [t for t in tasks if keyword.lower() in t.title.lower() or keyword.lower() in t.description.lower()]

You test it ✅. It works. Done.

And if it doesn’t? You don’t blindly change the code. You fix the spec.

Why This Works So Well (Especially with AI)

  • Smarter Code 🧠: AI + spec = less spaghetti code
  • Faster Turnaround 🚀: Less trial-and-error
  • Cross-Platform Ready 🔁: Regenerate the same logic across Python, JavaScript, etc.
  • Docs? Already Done 📄: Your specs are your docs
  • New Devs Onboard Faster ⏩: They read specs instead of reverse-engineering code
  • Fewer Bugs 🐞: Because clarity wins

Looking Ahead

Spec-first sets the stage for:

  • AI Agents: They need clear goals. Specs are those goals.
  • Full Automation: One spec to generate code, tests, docs, and maybe coffee (someday? ☕)
  • Long-Term Wins: Better tools = better implementations from the same spec
  • Reusable Patterns: Build your own spec library for repeatable features

TL;DR 💬

Spec-first isn’t about being slow or bureaucratic. It’s about being deliberate. You write your intention clearly — and then let the tools (and the AI) do the heavy lifting.

So next time before diving into code: pause, breathe, write that spec. Your future self (and your AI assistant) will thank you.

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