Working Prototypes Beat Specs

A PRD is a guessing game with shared vocabulary.

A prototype is a decision you can click.

The gap between heads

You write a spec. You think it's clear. You describe the flow, the edge cases, the states. You hand it to engineering.

They read it. They fill in the blanks you didn't know you left. They build what they understood.

Three weeks later, you're in a review meeting, looking at something that matches every word you wrote but misses the thing you meant.

The problem isn't the spec. The problem is that everyone reading a document is doing guesswork. They're filling gaps with their own assumptions. And those assumptions rarely match.

"You end up doing a bunch of guesswork and then people are surprised when the guesswork that other people are doing doesn't actually connect with the guesswork that they were doing in their head."

Logan Kilpatrick, Roo Cast S01E15

The spec felt complete when you wrote it. It wasn't. It was a scaffolding for assumptions.

The prototype forces the conversation

A prototype doesn't describe what you want. It shows what you want.

When you walk into a room with something clickable, the conversation changes. You're not debating interpretations. You're pointing at a screen saying "this button should do this" and watching whether it does.

The cost of getting to that point used to be high. You needed engineering time to build a throwaway. Or you needed to mock something in Figma and hope the static screens captured the flow well enough.

That cost has collapsed. Tools like Roo Code let you build something functional without writing production code yourself. You can generate a working prototype, click through it, find the holes, and iterate before engineering ever gets involved.

The prototype forces you to confront edge cases that disappear in mocks. What happens when this list is empty? What does the error state look like? Where does this data come from?

"It forces design and product to think through the experience edge cases that aren't evident on a mock."

Hannes Rudolph, Roo Cast S01E15

You find out what's missing when you try to use it, not when engineering asks "what should happen here?" two weeks into the build.

The handoff gets cleaner

The prototype isn't production code. It's not supposed to be.

But it gives engineering something concrete to work from. They can see the flow, click through the states, understand the logic. The handoff isn't "read this doc and build what you think it means." It's "here's what it should do; make it production-ready."

When the prototype lives in a repo, even as a rough draft, the artifacts are already there. Issues, commits, iteration history. Engineering can fork from something real instead of starting from interpreted text.

The tradeoff is time upfront. Building a prototype takes longer than writing a spec. But the time you spend building is time you're not spending in alignment meetings, redoing work, or debugging misunderstandings.

Why this matters for your workflow

If you're a PM or designer working with a small team, the leverage is significant. You stop being the person who hands off documents and waits. You become the person who shows up with something clickable and says "here's what I'm thinking."

"It's way easier to show up with something like a prototype and be like, 'Hey, here's what I'm thinking.' And there's much less guesswork in that."

Logan Kilpatrick, Roo Cast S01E15

For teams shipping 4-5 features a quarter, replacing even half of your spec-first workflows with prototype-first conversations can eliminate entire rounds of revision. The feedback happens before the build, not after.

You don't need to become an engineer to do this. You need a tool that lets you generate working code from intent. Roo Code gives you that: describe what you want, iterate on the output, and hand off something that works instead of something that hopes to be understood.

The default has shifted

The cost of bringing an idea to something you can touch is now low enough that it should be the default.

If you're still writing specs and hoping people interpret them correctly, try building one prototype instead. Click through it. Find the gaps. Then hand it off.

The guesswork disappears when everyone's looking at the same screen.

How Roo Code closes the loop on prototype-first workflows

Roo Code is an AI coding agent that closes the loop: it can propose code, run commands, execute tests, and iterate based on results. For prototype-first workflows, this means PMs and designers can describe what they want in natural language, watch Roo Code generate a working prototype, and then iterate on that prototype through conversation rather than code.

Because Roo Code operates with BYOK (bring your own key), you control your AI provider and spend tokens intentionally for outcomes. The prototype you build stays in your repo, with full commit history, ready for engineering to fork into production code.

The core shift: instead of writing specs that get interpreted, you generate prototypes that get clicked. Roo Code makes this workflow accessible to anyone who can describe what they want.

Spec-first vs. prototype-first workflows