How to Write a Build Spec for Your AI App (Beginner Guide): A beginner guide from the founder of GoodVibeSpecs

How do you start building an AI app when you have never built one before? Most people open ChatGPT, Cursor, Bolt, or Lovable and start typing. And most people end up frustrated.
Not because the AI tools are bad. Because the starting point was vague.
The real problem with vibe coding as a beginner
Vibe coding — describing what you want in plain English and letting AI generate the app — has completely changed what is possible for non-technical people.
A quarter of YC Winter 2025 startups had codebases that were 95% AI-generated. Andrej Karpathy, who coined the term in 2025, called it a fundamental shift in how software gets built. Collins Dictionary made it their Word of the Year.
But here is what nobody tells you when you are just starting out.
The AI is not the problem. Your starting point is.
When you open a new chat and type something like “build me an app that helps people find dog sitters,” the AI has to guess what you actually mean. It guesses your users. It guesses your features. It guesses your scope. And those guesses change with every message, so the build drifts, features appear from nowhere, and you end up going round in circles.
This is not a bug. It is what happens when you give any system vague input.
The fix is simple: write a build spec before you start.
The app that taught me everything
A while back I built TasteCheckApp It is a fun app where AI analyses your music playlists and you can battle a friend using a shareable remote link. Think Spotify Wrapped meets friendly rivalry.
But the build? That was a different story.
Because I started without a clear plan, decisions kept appearing mid-build that should have been made at the very start. How should the friend link work? What happens when someone does not have a streaming account? What does the comparison actually look like? Should users save results?
Each decision led to more decisions. The scope kept shifting. Features I thought would take an hour turned into rabbit holes. Things that seemed obvious at the start became genuinely complicated once the AI was halfway through building them.
By the end, I had an app that worked — but the journey was far messier than it needed to be.
And the whole time, one thought kept coming back: if only I had set this out properly at the start.
That frustration is exactly why I built GoodVibeSpecs

So what actually is a build spec?
A build spec is a short structured document that describes what your app is, who it is for, what it needs to do, and what the MVP actually includes.
Think of it as a brief for your AI. Instead of figuring everything out through a long chaotic chat, you give your AI tool a clear foundation to work from at the very beginning.
It does not need to be long. It does not need to be technical. It just needs to answer the right questions before the build starts.
In 2026, this has become a mainstream idea. Addy Osmani, a senior engineer at Google, published a detailed guide on writing specs for AI agents in January 2026 that was picked up by O’Reilly. The core message was simple: give your AI structured context, not vague instructions. Addy Osmani post

Why skipping the spec causes so much pain
When you open your AI tool and type “build me an app that does X,” the AI has to guess what you mean. It guesses your users. It guesses your features. It guesses your scope. And those guesses change with every message.
So the build drifts. Features appear that you did not ask for. Features you did ask for get missed or implemented inconsistently. You end up spending two hours correcting things instead of building.
The number one mistake beginners make is starting with vague prompts. Not because they are doing anything wrong, but because they simply do not know what to include yet.
That is the gap a build spec fills.

The 6 things a good beginner build spec includes
You do not need a 50-page product requirements document. For a beginner vibe coding project, a solid spec covers six things.

1. Your target user Who is this app actually for? Be specific. Not “people who like music” but “music fans aged 18 to 35 who want to compare their taste with friends in a fun and shareable way.” The more specific you are, the better the AI understands what decisions to make throughout the build.
2. The core problem What frustrating or painful thing does your app solve? Write it in one sentence. If you cannot write it in one sentence, the idea needs more clarity before you build anything.
3. Core features What are the three to five things the app must do to be useful? List them clearly. Everything else is a nice-to-have for later.
4. MVP scope What are you building first and what are you leaving out? This is the most important decision you can make before you start. Scope creep mid-build is the single biggest reason beginner projects stall.
5. User flow What does a user actually do from the moment they land on your app to the moment they get value? Map it out in plain English. Step one, step two, step three. Your AI will produce much more coherent output when it understands the full journey.
6. Build direction What kind of app is this? Web app, mobile, internal tool? Any preferences on stack or tools? Even rough answers here help the AI make better decisions throughout. A quick before and after Here is what a vague starting prompt looks like: “I want to build an app where people can compare their music taste and battle their friends.” And here is what a structured spec gives you instead: Target user: music fans who want a fun way to compare playlists with friends Core problem: there is no quick, shareable way to find out who has better music taste Core features: playlist analysis, taste score, shareable battle link, results comparison MVP scope: web app, screenshot upload, one vs one battle, shareable link — no accounts needed in v1 User flow: upload screenshot, get taste score, share link with friend, see side-by-side comparison, share result Build direction: web app, simple and fast, mobile-friendly That second version gives your AI something genuinely useful to work from. The output will be more consistent, more focused, and closer to what you actually imagined.

But why not just ask ChatGPT to figure it out as you go?
This is the question everyone asks. And it is completely fair.
The truth is, you can. Plenty of people do. But most beginners who try this approach hit the same wall.
They do not know what details to include upfront, so the AI fills in the gaps with its own assumptions. Those assumptions change from session to session. The build loses consistency. Important product decisions get buried in a long chat thread and forgotten.
A fuzzy idea is fine for daydreaming. It is rough for building.
GoodVibeSpecs does not replace your AI coding tool. It helps you get better results from it by giving it a stronger starting point.

How GoodVibeSpecs helps you skip the painful part
GoodVibeSpecs was built specifically for beginners and non-technical founders who have a great idea but are not sure how to turn it into a clear build plan.
You describe your app idea — even if it is still rough and incomplete — and GoodVibeSpecs turns it into a structured spec covering your target users, core features, MVP scope, user flow, and product direction.
Then you take that spec and feed it straight into ChatGPT, Cursor, Bolt, Lovable, or whatever AI tool you use.
The whole thing costs £1.99 per spec. Less than a coffee, and it will save you hours.

I built it because I wish it had existed when I was building TasteCheckApp. The messy mid-build decisions, the scope drift, the hours of back-and-forth — most of that was avoidable. A solid spec at the start would have changed everything.
If you are about to start building with AI, do not skip this step.
Generate your spec for just £1.99 → GoodVibeSpecs

Quick summary
Most beginner AI builds go wrong because of vague starting instructions, not bad AI tools
A build spec gives your AI a clearer foundation before the build starts.
A good beginner spec covers: target user, core problem, core features, MVP scope, user flow, and build direction
GoodVibeSpecs turns your rough idea into a structured spec in minutes for just £1.99
Better input leads to better AI output — every time

This article was written by the founder of GoodVibeSpecs and TasteCheckApp.