spec-driven-development

spec-driven-development is a skill for Claude Code from nota-america/forgecat-agent-profiles. It costs 81 tokens per session (2,679 once invoked), scanned A, a copy of spec-driven-development, Apache-2.0.

A development process that writes and reviews a clear specification before coding begins.

In plain words
What is it for?
It helps define what to build, why it is needed, how it will work, and how completion will be checked before implementation.
Why use it?
It reduces misunderstandings when requirements are vague or a change affects several parts of a project.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

Good fit It helps define what to build, why it is needed, how it will work, and how completion will be checked before implementation.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/nota-america/forgecat-agent-profiles/spec-driven-development
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add nota-america/forgecat-agent-profiles --skill spec-driven-development
Clone the repo
git clone --depth 1 https://github.com/nota-america/forgecat-agent-profiles

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for spec-driven-development

README.md
[![agentmods](https://agentmods.dev/badge/skills/nota-america/forgecat-agent-profiles/spec-driven-development/github.svg)](https://agentmods.dev/skills/nota-america/forgecat-agent-profiles/spec-driven-development)
Your own site
<a href="https://agentmods.dev/skills/nota-america/forgecat-agent-profiles/spec-driven-development"><img src="https://agentmods.dev/badge/skills/nota-america/forgecat-agent-profiles/spec-driven-development/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for spec-driven-development

Your own site · 80×15
<a href="https://agentmods.dev/skills/nota-america/forgecat-agent-profiles/spec-driven-development"><img src="https://agentmods.dev/badge/skills/nota-america/forgecat-agent-profiles/spec-driven-development.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 81 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,679 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 100% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00081 $0.02679
Opus 5.5 $0.00032 $0.01072
Sonnet 5.5 $0.00016 $0.00536
Haiku 4.5 $0.00008 $0.00268

Measured 1mo ago against content hash 6c019847f775, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

spec-driven-development scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

100% identical to spec-driven-development — 62 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

profiles/addyosmani/agent-skills/for-claude/.claude/skills/spec-driven-development/SKILL.md · 257 lines

How it starts

The opening of the file, as written. The whole thing — 257 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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

Phase 0: Scope Check

Most requests describe one capability. If this one does, skip this phase and go straight to Specify — Phase 0 exists for the exception, not the rule, and it puts no hierarchy on single-capability features.

Detection. Decompose before specifying when a single requirement bundles several independently testable capabilities:

  • The requirement names distinct capabilities with their own consumers or data (e.g. identity, billing, notifications, reporting)
  • Acceptance criteria cluster into groups that could ship and be verified separately
  • One capability could be cut or replaced without rewriting the others' requirements

Propose a capability map before writing any spec. Small and reviewable — a module table plus a build order, not a project plan:

# Capability Map: [Initiative Name]

| Module id | Responsibility | Depends on |
|---|---|---|
| identity | Accounts, sessions, SSO | — |
| billing | Plans, invoices, payments | identity |
| notifications | Email and webhook fan-out | identity |
| reporting | Usage dashboards | billing, notifications |

Build order: identity → billing, notifications → reporting

Read the full file on GitHub · 257 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 1mo ago Changed · +54 lines · +38 tokens per session 6c019847f775
  2. 1mo ago First seen · 203 lines · 43 tokens per session scan A fabf224ed1c0

Subscribe to this mod's changes

spec-driven-development is a skill published in the GitHub repository nota-america/forgecat-agent-profiles (93 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 81 tokens to every session and 2,679 once invoked, about $0.0003 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to spec-driven-development, differing in 62 lines, and is treated as a copy.