Agent skill

Spec Writing

Convert an approved PRD or clear requirements into an implementation-ready technical spec with scope, interfaces, and acceptance criteria.

MITAuto-check passedProduct & Project Management

Install Spec Writing

skills CLI

$ npx skills add itseffi/agentic-os --skill spec-writing -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI

$ gh skill install itseffi/agentic-os spec-writing --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy

$ git clone --depth 1 https://github.com/itseffi/agentic-os.git skills-src && mkdir -p .claude/skills && cp -r skills-src/.agents/skills/spec-writing .claude/skills/spec-writing && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Paste into Claude Code

Install the "spec-writing" agent skill from https://github.com/itseffi/agentic-os/tree/main/.agents/skills/spec-writing into .claude/skills/spec-writing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "spec-writing", then confirm the skill loads.

Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

$skill-installer

$skill-installer install https://github.com/itseffi/agentic-os/tree/main/.agents/skills/spec-writing

Type this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.

skills CLI

$ npx skills add itseffi/agentic-os --skill spec-writing -a codex

Project install goes to .agents/skills/; add -g for ~/.codex/skills/.

GitHub CLI

$ gh skill install itseffi/agentic-os spec-writing --agent codex

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/itseffi/agentic-os.git skills-src && mkdir -p .agents/skills && cp -r skills-src/.agents/skills/spec-writing .agents/skills/spec-writing && rm -rf skills-src

Use ~/.agents/skills/ instead of .agents/skills for a personal install.

Codex skills documentation · loads skills from .agents/skills/

Paste into Codex

Install the "spec-writing" agent skill from https://github.com/itseffi/agentic-os/tree/main/.agents/skills/spec-writing into .agents/skills/spec-writing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "spec-writing", then confirm the skill loads.

Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add itseffi/agentic-os --skill spec-writing -a cursor

Project install goes to .agents/skills/; add -g for ~/.cursor/skills/.

GitHub CLI

$ gh skill install itseffi/agentic-os spec-writing --agent cursor

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/itseffi/agentic-os.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/.agents/skills/spec-writing .cursor/skills/spec-writing && rm -rf skills-src

Use ~/.cursor/skills/ instead of .cursor/skills for a personal install.

Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/

Paste into Cursor

Install the "spec-writing" agent skill from https://github.com/itseffi/agentic-os/tree/main/.agents/skills/spec-writing into .cursor/skills/spec-writing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "spec-writing", then confirm the skill loads.

Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

gemini skills install

$ gemini skills install https://github.com/itseffi/agentic-os.git --path .agents/skills/spec-writing

--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.

skills CLI

$ npx skills add itseffi/agentic-os --skill spec-writing -a gemini-cli

Project install goes to .agents/skills/; add -g for ~/.gemini/skills/.

GitHub CLI

$ gh skill install itseffi/agentic-os spec-writing --agent gemini-cli

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/itseffi/agentic-os.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/.agents/skills/spec-writing .gemini/skills/spec-writing && rm -rf skills-src

Use ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.

Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/

Paste into Gemini CLI

Install the "spec-writing" agent skill from https://github.com/itseffi/agentic-os/tree/main/.agents/skills/spec-writing into .gemini/skills/spec-writing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "spec-writing", then confirm the skill loads.

Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

GitHub CLI

$ gh skill install itseffi/agentic-os spec-writing

Installs for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).

skills CLI

$ npx skills add itseffi/agentic-os --skill spec-writing -a github-copilot

Project install goes to .agents/skills/; add -g for ~/.copilot/skills/.

Manual copy

$ git clone --depth 1 https://github.com/itseffi/agentic-os.git skills-src && mkdir -p .github/skills && cp -r skills-src/.agents/skills/spec-writing .github/skills/spec-writing && rm -rf skills-src

Use ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.

GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/

Paste into GitHub Copilot

Install the "spec-writing" agent skill from https://github.com/itseffi/agentic-os/tree/main/.agents/skills/spec-writing into .github/skills/spec-writing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "spec-writing", then confirm the skill loads.

GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

skills CLI

$ npx skills add itseffi/agentic-os --skill spec-writing -a opencode

OpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.

GitHub CLI

$ gh skill install itseffi/agentic-os spec-writing --agent opencode

Project scope by default (.agents/skills/); add --scope user for a personal install.

Manual copy

$ git clone --depth 1 https://github.com/itseffi/agentic-os.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/.agents/skills/spec-writing .opencode/skills/spec-writing && rm -rf skills-src

Use ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.

OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/

Paste into OpenCode

Install the "spec-writing" agent skill from https://github.com/itseffi/agentic-os/tree/main/.agents/skills/spec-writing into .opencode/skills/spec-writing/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "spec-writing", then confirm the skill loads.

OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.

Facts

Skill name: spec-writing
GitHub stars: 115
Token cost: ~464 tokens
SKILL.md length: 156 words
Files: 2
Skills in repo: 29
Repo updated: Oct 7, 2026
First seen: Oct 7, 2026
Licence: MIT

At a glance

Convert an approved PRD or clear requirements into an implementation-ready technical spec with scope, interfaces, and acceptance criteria.

Works in 4 steps: Validate inputs → Define scope boundaries → Define solution design → …
Tasks that involve PRD writing
SKILL.md covers The Process, Output Format, Quality Bar and When to Use, plus 1 more section
Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Spec Writing is an agent skill from itseffi/agentic-os. Convert an approved PRD or clear requirements into an implementation-ready technical spec with scope, interfaces, and acceptance criteria.

Its SKILL.md is about 460 tokens, which your agent loads only when the skill is triggered. The skill folder holds 2 other files (for example `agents/openai.yaml`).

It sits in Product & Project Management, covering PRD writing and User stories. The repository describes itself as: Agentic personal OS to automate high-leverage workflows with Codex, Claude Code, Pi, OpenClaw and other coding agents/ runtime platforms. The licence is MIT.

When your agent uses it

Tasks that involve PRD writing
Tasks that involve User stories

Example prompts

“/spec-writing”

Workflow steps

4 steps, taken from the step headings in SKILL.md.

Validate inputs
Define scope boundaries
Define solution design
Define acceptance and verification

What it can do on your machine

Read from SKILL.md and the folder at commit e54d0ac. It shows what the files ask for, not the result of running them.

Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md (its code samples are markdown).
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Spec Writing loads about 464 tokens when it runs. Until then it costs about 38 tokens; SKILL.md has 156 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it: ~38
When it runs · the whole SKILL.md, loaded when a task matches: ~464

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from itseffi/agentic-os at commit e54d0ac, republished under its MIT licence (© itseffi). 156 words, ~464 tokens.

Download SKILL.mdSave it as .claude/skills/spec-writing/SKILL.md (or your agent's skills folder). This skill also uses 1 other file; get the full folder from GitHub.

name: spec-writing
description: Convert an approved PRD or clear requirements into an implementation-ready technical spec with scope, interfaces, and acceptance criteria.

Spec Writing

Use this skill to produce an implementation-ready spec before planning or coding.

The Process

Step 1: Validate inputs

Require one of:

approved PRD
clear requirements with goals and constraints

If inputs are missing or ambiguous, list assumptions and open questions first.

Step 2: Define scope boundaries

Document:

in scope
out of scope
constraints (time, dependencies, compliance, platform)

Step 3: Define solution design

Specify:

architecture overview (high-level components)
interfaces/contracts
data model changes
rollout and migration approach

Step 4: Define acceptance and verification

Include:

acceptance criteria (testable)
non-functional expectations (performance, security, reliability)
verification commands/checks required before completion

Output Format

markdown

# [Feature Name] Technical Spec

## Goal
[What this spec delivers and why]

## Scope
- In scope:
- Out of scope:
- Constraints:

## Design
- Architecture:
- Interfaces/contracts:
- Data model changes:
- Migration/rollout:

## Risks and Dependencies
- Risks:
- Dependencies:
- Mitigations:

## Acceptance Criteria
- AC1:
- AC2:
- AC3:

## Verification Plan
- Required checks:
- Commands:
- Evidence to capture:

## Open Questions
- Q1:
- Q2:

Quality Bar

No vague placeholders in final output
Acceptance criteria must be measurable
Verification plan must include explicit commands

When to Use

Use this skill when the task directly matches the workflow described above.

When Not to Use

Do not use this skill when the request is unrelated, low-stakes, or better handled by a simpler direct response.

Files

SKILL.md and 1 other file in .agents/skills/spec-writing of itseffi/agentic-os.

SKILL.md
agents/openai.yaml

Open the folder on GitHubat commit e54d0ac

Compare with similar skills

Spec Writing next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Spec Writing compared with similar skills
Skill	Stars	Used in	Tokens	Auto-check	Licence	Repo updated
Spec Writing this skillitseffi/agentic-os	115	—	~464	Automated safety check: Pass	MIT	yesterday
Ralph Tui Create Beadssubsy/ralph-tui	2.5k	1 repos	~2.6k	Automated safety check: Pass	MIT	1 mo ago
Ralph Tui Create Beads Rustsubsy/ralph-tui	2.5k	1 repos	~2.8k	Automated safety check: Pass	MIT	1 mo ago
Ralph Tui Create JSONsubsy/ralph-tui	2.5k	1 repos	~2.6k	Automated safety check: Pass	MIT	1 mo ago
To Prdywwynm/EverythingDone	144	11 repos	~777	Automated safety check: Pass	GPL-3.0	24 days ago
Ralphjulianromli/opencode-template	144	1 repos	~1.1k	Automated safety check: Pass	None	8 mo ago

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Questions about Spec Writing

What does Spec Writing do?

Convert an approved PRD or clear requirements into an implementation-ready technical spec with scope, interfaces, and acceptance criteria. Spec Writing is an agent skill from itseffi/agentic-os. Convert an approved PRD or clear requirements into an implementation-ready technical spec with scope, interfaces, and acceptance criteria.

When should I use Spec Writing?

Spec Writing fits situations like: tasks that involve PRD writing; tasks that involve User stories.

How do I install Spec Writing in Claude Code?

Run `npx skills add itseffi/agentic-os --skill spec-writing -a claude-code`. Or copy the skill folder (.agents/skills/spec-writing in itseffi/agentic-os) into .claude/skills/spec-writing in your project. Claude Code loads it when a task matches its description.

How do I install Spec Writing in Codex?

Run `npx skills add itseffi/agentic-os --skill spec-writing -a codex`. Or copy the skill folder (.agents/skills/spec-writing in itseffi/agentic-os) into .agents/skills/spec-writing in your project. Codex loads it when a task matches its description.

Can I use Spec Writing in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add itseffi/agentic-os --skill spec-writing -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/spec-writing, .gemini/skills/spec-writing, .github/skills/spec-writing and .opencode/skills/spec-writing in your project.

What does Spec Writing need to run?

SKILL.md names no scripts, command-line tools or credentials: Spec Writing is instructions for the agent only.

Does Spec Writing access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Spec Writing safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Spec Writing use?

Spec Writing is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Spec Writing use?

About 464 tokens (SKILL.md is roughly 1.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Spec Writing?

Skills that share tags, products or a category with Spec Writing: Ralph Tui Create Beads (subsy/ralph-tui, 2.5k stars), Ralph Tui Create Beads Rust (subsy/ralph-tui, 2.5k stars), Ralph Tui Create JSON (subsy/ralph-tui, 2.5k stars) and To Prd (ywwynm/EverythingDone, 144 stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Spec Writing?

itseffi (a GitHub user) maintains it in itseffi/agentic-os, which has 115 GitHub stars. The repository holds 29 skills in this directory. The repository was last updated on October 7, 2026.

Source: itseffi/agentic-os on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.

Install Spec Writing

Facts

At a glance

What it does

When your agent uses it

Example prompts

Workflow steps

What it can do on your machine

Tool permissions

Runs code

Network

Credentials

Context cost

Safety

SKILL.md

Spec Writing

The Process

Step 1: Validate inputs

Step 2: Define scope boundaries

Step 3: Define solution design

Step 4: Define acceptance and verification

Output Format

Quality Bar

When to Use

When Not to Use

Files

Compare with similar skills

Similar skills

More from itseffi/agentic-os

Related

Questions about Spec Writing