spec-driven

Write a scoped spec with goals, non-goals, and acceptance criteria before implementation.

2|Updated Apr 10, 2026
One-click install
npx skills add https://github.com/t0lab/harness-kit --skill spec-driven-t0lab
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: spec-driven
Source: https://github.com/t0lab/harness-kit/tree/main/.agents/skills/spec-driven
Command: npx skills add https://github.com/t0lab/harness-kit --skill spec-driven-t0lab

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Prevents implementation from becoming the de facto specification for non-trivial work by insisting on a written, scoped specification before planning and execution. It reduces scope drift, unclear acceptance criteria, and accidental policy decisions encoded in code rather than documents.

Core Features & Use Cases

  • Scope enforcement: Guides authors to declare explicit goals, non-goals, and acceptance criteria so reviewers and implementers share a single source of truth.
  • Spec hygiene: Recommends the minimal spec type (product spec, design doc, or both) and ensures the spec is executable by downstream planning agents.
  • Gate planning: Defines the required sequence: explore, write/update spec, align, plan, then implement — preventing premature implementation.
  • Use Case: When adding a user-facing feature or changing an API, use this skill to produce a product or design spec that reviewers can validate before work begins.

Quick Start

Use the spec-driven skill to write a concise product or design spec that states the problem, goals, non-goals, acceptance criteria, and the minimal solution sketch.

Frequently Asked Questions about spec-driven

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I prevent implementation from becoming the de facto specification for non-trivial changes?

To prevent implementation becoming the de facto specification, you must insist on a written, scoped specification before planning and execution. This reduces scope drift, unclear acceptance criteria, and accidental policy decisions encoded in code.

What should a product spec or design doc include to prevent scope drift?

A product spec or design doc should include the problem, goals, non-goals, acceptance criteria, and a minimal solution sketch. Declaring these explicitly ensures reviewers and implementers share a single source of truth.

How do I write acceptance criteria for API changes and multi-file refactoring workflows?

Write acceptance criteria for API changes by applying a spec-driven sequence: explore, write or update the spec, align, plan, then implement. This gating sequence defines required steps and prevents premature implementation.

When do I need a design doc versus a product spec for feature development?

You need a design doc versus a product spec based on the change type. Spec hygiene recommends the minimal spec type required—product spec, design doc, or both—ensuring the document is executable by downstream planning agents.

Does spec-driven planning work for multi-file workflows where goals may drift?

Spec-driven planning works for multi-file workflows by guiding authors to declare explicit goals, non-goals, and acceptance criteria. This scope enforcement ensures reviewers and implementers share a single source of truth.

Why does my feature development process have accidental policy decisions encoded in code?

Feature development has accidental policy decisions encoded in code when implementation becomes the de facto specification. Insisting on a written specification before planning and execution prevents these accidental policy decisions.