agents-at-scale-ark: Skill for Claude Code

.claude/skills/openspec-onboard/SKILL.md

openspec-onboard is a skill for Claude Code from mckinsey/agents-at-scale-ark. It costs 26 tokens per session (3,360 once invoked), scanned A, a copy of openspec-onboard, Apache-2.0.

A guided lesson that takes a developer through a complete OpenSpec workflow while making a real change in a codebase.

In plain words
What is it for?
Use it to learn structured change planning and apply that workflow to a small task in an existing project.
Why use it?
It helps first-time users learn OpenSpec by doing the full process, from planning through implementation and archiving.

Skill for Claude Code

Written for Claude Code: installed under .claude/.

This is mckinsey/agents-at-scale-ark's own configuration. It tells Claude Code how to work on agents-at-scale-ark itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything agents-at-scale-ark configures →

Reuse

Borrowing it

Nothing to install: this file belongs to mckinsey/agents-at-scale-ark. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/mckinsey/agents-at-scale-ark/main/.claude/skills/openspec-onboard/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/mckinsey/agents-at-scale-ark

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 openspec-onboard

README.md
[![agentmods](https://agentmods.dev/badge/skills/mckinsey/agents-at-scale-ark/openspec-onboard/github.svg)](https://agentmods.dev/skills/mckinsey/agents-at-scale-ark/openspec-onboard)
Your own site
<a href="https://agentmods.dev/skills/mckinsey/agents-at-scale-ark/openspec-onboard"><img src="https://agentmods.dev/badge/skills/mckinsey/agents-at-scale-ark/openspec-onboard/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 openspec-onboard

Your own site · 80×15
<a href="https://agentmods.dev/skills/mckinsey/agents-at-scale-ark/openspec-onboard"><img src="https://agentmods.dev/badge/skills/mckinsey/agents-at-scale-ark/openspec-onboard.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 26 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,360 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 73% 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 $0.00026 $0.03360
Opus 5 $0.00013 $0.01680
Sonnet 5 $0.00005 $0.00672
Haiku 4.5 $0.00003 $0.00336

Measured 8d ago against content hash d3f8c1933b70, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-12, from the pricing page.

Security

Grade A, and why

openspec-onboard 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 8d 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

73% identical to openspec-onboard — 100 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.

.claude/skills/openspec-onboard/SKILL.md · 555 lines

How it starts

The opening of the file, as written. The whole thing — 555 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Guide the user through their first complete OpenSpec workflow cycle. This is a teaching experience—you'll do real work in their codebase while explaining each step.


Preflight

Before starting, check if the OpenSpec CLI is installed:

# Unix/macOS
openspec --version 2>&1 || echo "CLI_NOT_INSTALLED"
# Windows (PowerShell)
# if (Get-Command openspec -ErrorAction SilentlyContinue) { openspec --version } else { echo "CLI_NOT_INSTALLED" }

If CLI not installed:

OpenSpec CLI is not installed. Install it first, then come back to /opsx:onboard.

Stop here if not installed.


Phase 1: Welcome

Display:

## Welcome to OpenSpec!

I'll walk you through a complete change cycle—from idea to implementation—using a real task in your codebase. Along the way, you'll learn the workflow by doing it.

**What we'll do:**
1. Pick a small, real task in your codebase
2. Explore the problem briefly
3. Create a change (the container for our work)
4. Build the artifacts: proposal → specs → design → tasks
5. Implement the tasks
6. Archive the completed change

**Time:** ~15-20 minutes

Let's start by finding something to work on.

Phase 2: Task Selection

Codebase Analysis

Scan the codebase for small improvement opportunities. Look for:

  1. TODO/FIXME comments - Search for TODO, FIXME, HACK, XXX in code files
  2. Missing error handling - catch blocks that swallow errors, risky operations without try-catch
  3. Functions without tests - Cross-reference src/ with test directories
  4. Type issues - any types in TypeScript files (: any, as any)
  5. Debug artifacts - console.log, console.debug, debugger statements in non-debug code
  6. Missing validation - User input handlers without validation

Also check recent git activity:

# Unix/macOS
git log --oneline -10 2>/dev/null || echo "No git history"
# Windows (PowerShell)
# git log --oneline -10 2>$null; if ($LASTEXITCODE -ne 0) { echo "No git history" }

Read the full file on GitHub · 555 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. 8d ago First seen · 555 lines · 26 tokens per session scan A d3f8c1933b70

Subscribe to this mod's changes

openspec-onboard is a skill published in the GitHub repository mckinsey/agents-at-scale-ark (423 stars, last pushed today), licensed Apache-2.0. It adds 26 tokens to every session and 3,360 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. It is 73% identical to openspec-onboard, differing in 100 lines, and is treated as a copy.

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