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

.claude/skills/chainsaw/SKILL.md

ark-chainsaw-testing is a skill for Claude Code from mckinsey/agents-at-scale-ark. It costs 35 tokens per session (1,132 once invoked), scanned A, original, Apache-2.0.

A testing guide for writing and running Ark end-to-end tests with Chainsaw and a mock language model. End-to-end tests check complete workflows across several system parts.

In plain words
What is it for?
It is for running selected or full test suites, creating test manifests, testing queries, and investigating failed Kubernetes tests.
Why use it?
It provides repeatable test structures and debugging commands for finding failures in Ark resources and workflows.

Skill for Claude Code

Written for Claude Code: installed under .claude/. Also seen: mentions CLAUDE.md.

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 →

Needs its repository: it runs a file that does not travel with it, so clone the repository first. The line is chainsaw test ./tests/query-parameter-ref --fail-fast.

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/chainsaw/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

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README.md
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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.

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Your own site · 80×15
<a href="https://agentmods.dev/skills/mckinsey/agents-at-scale-ark/chainsaw"><img src="https://agentmods.dev/badge/skills/mckinsey/agents-at-scale-ark/chainsaw.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 35 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,132 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. Third-party audits
  • NVIDIA SkillSpector pass 7 Sept 2026
How audits are shown
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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00035 $0.01132
Opus 5 $0.00017 $0.00566
Sonnet 5 $0.00007 $0.00226
Haiku 4.5 $0.00003 $0.00113

Measured 6d ago against content hash a6a23a255bfe, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

ark-chainsaw-testing 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 6d 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.

.claude/skills/chainsaw/SKILL.md · 162 lines

How it starts

The opening of the file, as written. The whole thing — 162 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Ark Chainsaw Testing

Run and write Chainsaw e2e tests for Ark resources.

Running Tests

# Run all standard tests
(cd tests && chainsaw test --selector 'standard')

# Run specific test
chainsaw test ./tests/query-parameter-ref --fail-fast

# Debug mode - keep resources on failure
chainsaw test ./tests/query-parameter-ref --skip-delete --pause-on-failure

Writing Tests

Reference tests/CLAUDE.md for comprehensive patterns.

For a complete working example that shows the correct patterns for writing tests, see examples.md.

Test Structure

tests/my-test/
├── chainsaw-test.yaml      # Test definition
├── mock-llm-values.yaml    # Mock LLM config (if needed)
├── README.md               # Required documentation
└── manifests/
    ├── a03-model.yaml      # Model before Agent
    ├── a04-agent.yaml      # Agent before Query
    └── a05-query.yaml      # Query last

Antipatterns

kubectl wait for CRD conditions

Never use kubectl wait --for=condition=Established to check CRD readiness. This command crashes with a type error when .status.conditions is nil (a known kubectl bug: kubernetes/kubernetes#66439):

error: .status.conditions accessor error: <nil> is of the type <nil>, expected []interface{}

Use a chainsaw assert with JMESPath instead — it polls gracefully and waits for the field to appear:

# Bad - crashes if .status.conditions is nil
- script:
    content: |
      kubectl apply -f my-crd.yaml
      kubectl wait --for=condition=Established crd/my-crd.example.com --timeout=60s

# Good - polls until condition appears, no nil crash
- script:
    content: |
      kubectl apply -f my-crd.yaml
- assert:
    resource:
      apiVersion: apiextensions.k8s.io/v1
      kind: CustomResourceDefinition
      metadata:
        name: my-crd.example.com
      status:
        (conditions[?type == 'Established']):
          - status: "True"

This pattern converts a brittle timeout into an explicit condition check. The same applies to any resource whose .status.conditions may start as nil.

Read the full file on GitHub · 162 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

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. 6d ago First seen · 162 lines · 35 tokens per session scan A a6a23a255bfe

Subscribe to this mod's changes

ark-chainsaw-testing is a skill published in the GitHub repository mckinsey/agents-at-scale-ark (422 stars, last pushed today), licensed Apache-2.0. It adds 35 tokens to every session and 1,132 once invoked, about $0.0002 per session on Opus 5. 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 2026-09-03.

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