Spec Driven Development

Before you write a single line of code, this skill makes you write a spec that defines what you're building, why, and how you'll know it's done. It uses a four phase gate (specify, plan, tasks, implement) where you can't move forward until the human approves each stage. The real value is in surfacing assumptions early. It forces you to list what you're assuming about the tech stack, architecture, and requirements before proceeding, which catches misunderstandings when they're cheap to fix instead of after you've written 500 lines in the wrong direction. Skip it for typo fixes, use it when touching multiple files or making architectural calls.

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last updated: Aug 21, 2026

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Install

$ npx -y skills add addyosmani/agent-skills --skill spec-driven-development --agent claude-code

Installs into .claude/skills of the current project.

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Spec-Driven Development

Overview

Write a structured specification before writing any code. The spec is the shared source of truth between you and the human engineer — it defines what we're building, why, and how we'll know it's done. Code without a spec is guessing.

When to Use

Starting a new project or feature
Requirements are ambiguous or incomplete
The change touches multiple files or modules
You're about to make an architectural decision
The task would take more than 30 minutes to implement

When NOT to use: Single-line fixes, typo corrections, or changes where requirements are unambiguous and self-contained.

The Gated Workflow

Spec-driven development has four phases, preceded by a scope check (Phase 0) that activates only when one request bundles several independently testable capabilities. Do not advance to the next phase until the current one is validated.

SPECIFY ──→ PLAN ──→ TASKS ──→ IMPLEMENT
   │          │        │          │
   ▼          ▼        ▼          ▼
 Human      Human    Human      Human
 reviews    reviews  reviews    reviews