A software-design step that turns an approved product requirements document and system architecture into detailed implementation and test documents. It covers interfaces, data, system states, errors, security, and testing.

Use it to create `docs/SDD.md` and `docs/TEST.md` from existing project documents. It helps define module responsibilities, database details, state changes, error handling, and test cases.

It removes the gap between a high-level architecture and work developers can implement and verify. It also records the expected behavior before coding begins.

sdd — Skill for Claude Code and Codex by AlanHuang168

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 AlanHuang168/AI-Project-Workflow --skill sdd

Clone the repo

git clone --depth 1 https://github.com/AlanHuang168/AI-Project-Workflow

Made for: Claude Code, Codex.

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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/alanhuang168/ai-project-workflow/sdd/github.svg)](https://agentmods.dev/skills/alanhuang168/ai-project-workflow/sdd)

Your own site

<a href="https://agentmods.dev/skills/alanhuang168/ai-project-workflow/sdd"><img src="https://agentmods.dev/badge/skills/alanhuang168/ai-project-workflow/sdd/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/alanhuang168/ai-project-workflow/sdd"><img src="https://agentmods.dev/badge/skills/alanhuang168/ai-project-workflow/sdd.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 684 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 original No closer match found 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.

Model	Per session	Once invoked
Fable 5.1	$0.00000	$0.00684
Opus 5	$0.00000	$0.00342
Sonnet 5	$0.00000	$0.00137
Haiku 4.5	$0.00000	$0.00068

Measured 9d ago against content hash 0a77812e55d6, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

sdd 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 9d 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.

adapters/catpaw/.catpaw/skills/sdd/SKILL.md · 86 lines

How it starts

The opening of the file, as written. The whole thing — 86 lines — stays where its author put it; the contents beside it link to each section on GitHub.

name: sdd description: Create detailed design and test design from PRD and Architecture, covering interfaces, data structures, database design, module responsibilities, state transitions, error handling, security, and tests. Use when the user asks for detailed design or invokes /sdd. version: 1.0.0 stage: sdd

Goal

Produce docs/SDD.md and docs/TEST.md with enough detail to guide implementation and verification.

Use Cases

The user invokes /sdd.
The user asks to create SDD and Test Plan.
Architecture is approved and must be translated into interfaces, data, state, and tests.

Preconditions

docs/PRD.md exists and is not empty.
docs/ARCH.md exists and is not empty.
Workflow state shows hld complete unless the user explicitly approves a skip and the reason is recorded.

Required Context

AGENTS.md
.ai-workflow/state.json
core/rules/document-priority.md
core/templates/SDD.template.md
core/templates/TEST.template.md
docs/PRD.md
docs/ARCH.md

Inputs

Approved PRD and Architecture.
User-provided implementation boundaries, compatibility needs, and test environment notes.

Allowed Changes

docs/SDD.md
docs/TEST.md
.ai-workflow/state.json
Do not write business code.

Steps

Read PRD and Architecture and confirm that requirements, architecture, and interface contracts are consistent.
Design module responsibilities, interfaces, data structures, database design, state transitions, error handling, security design, logging and observability, compatibility, and implementation order.
Use pseudocode or flow descriptions for key algorithms. If signatures are needed, treat them as contracts, not implementation.
Design success, boundary, and failure tests for each key interface.
Create acceptance mapping from requirements to tests.
Write both docs/SDD.md and docs/TEST.md.
Update workflow state: documents.sdd = "complete", documents.test = "complete", add sdd to completedStages, set currentStage = "impl", and update the timestamp.

Read the full file on GitHub · 86 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.

9d ago First seen · 86 lines · 0 tokens per session scan A 0a77812e55d6

Subscribe to this mod's changes

sdd is a skill published in the GitHub repository AlanHuang168/AI-Project-Workflow (28 stars, last pushed 1mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 684 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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