specsy

Definition

What is a Claude Code spec?

A Claude Code spec is a markdown document that gives Claude Code a complete, ordered plan for building a specific app. It includes every architectural decision, the full build sequence, the exact commands to run, and the gotchas that would otherwise derail a build halfway through. You paste it into Claude Code, and Claude does the actual coding while following the spec's instructions.

In shorter form: a spec is the brief that removes all ambiguity from a Claude Code session.

What's inside a spec

A typical spec contains:

  • What you're building — a concrete product description, not a vibe
  • Tech stack decisions, already made — framework, database, styling, deploy target, all locked
  • A step-by-step build sequence — phases in order, with the exact commands to run at each step
  • Known failure points and their workarounds — the things that go wrong for everyone, called out before you hit them
  • Success criteria — how you know the build is done and working

A good spec reads less like documentation and more like an architect's plans. The decisions are already made. Your job, and Claude's, is to execute.

Not a spec

A spec is not:

  • A vague prompt like "build me a todo app"
  • A GitHub template repo
  • A tutorial video or blog post
  • A list of features

All of those leave too many decisions open. Claude Code is extremely capable but pragmatic: if your description is loose, it will make a hundred architectural decisions on your behalf. Sometimes those decisions are fine. Often they aren't, and you end up fighting Claude's choices halfway through the build. A spec eliminates the guessing.

Why specs exist as a format

Two things happened around late 2025. Claude Code got good enough that an average person, with no coding experience, could realistically build a working app in a weekend. And it became clear that the bottleneck wasn't Claude: it was the brief. A tight, well-structured brief produced apps that worked. A loose one produced expensive disappointments.

Specs are the format that emerged to solve that. They're also the unit of work that specsy sells.

Related

  • How specsy works — the three-step process for buying a spec and using it
  • Browse specs — the specs currently available on specsy
  • About specsy — why the platform exists and how verification works