Borrowing it
Nothing to install: this file belongs to Cratis/VerticalSlices. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/Cratis/VerticalSlices/main/.ai/skills/cratis-vertical-slice/SKILL.mdgit clone --depth 1 https://github.com/Cratis/VerticalSlicesWrote 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.
[](https://agentmods.dev/skills/cratis/verticalslices/cratis-vertical-slice)<a href="https://agentmods.dev/skills/cratis/verticalslices/cratis-vertical-slice"><img src="https://agentmods.dev/badge/skills/cratis/verticalslices/cratis-vertical-slice/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.
<a href="https://agentmods.dev/skills/cratis/verticalslices/cratis-vertical-slice"><img src="https://agentmods.dev/badge/skills/cratis/verticalslices/cratis-vertical-slice.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00089 | $0.01568 |
| Opus 5.5 | $0.00036 | $0.00627 |
| Sonnet 5.5 | $0.00018 | $0.00314 |
| Haiku 4.5 | $0.00009 | $0.00157 |
Grade A, and why
cratis-vertical-slice 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.
This is a copy
100% identical to cratis-vertical-slice — 4 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.
How it starts
The opening of the file, as written. The whole thing — 208 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Core principle
A vertical slice contains everything for a single behavior: the command or query, the events it produces, the projections that build read models, the React component, and the specs. Everything lives together because everything changes together.
One feature folder → many slices.
One slice folder → one .cs file (all backend) + one .tsx file (frontend).
Step 1 — Identify the feature and slice type
First, name the feature (a domain noun, pluralized) and identify the slice type:
| Slice type | What it does | Key artifacts |
|---|---|---|
| State Change | Mutates system state | Command + events + validators/constraints |
| State View | Projects events into queryable data | Read model + projection + queries |
| Automation | Reacts to events, makes decisions | Reactor + optional local read models |
| Translation | Adapts events between slices | Reactor → triggers commands in own slice |
Step 2 — Create the folder structure
The feature folder lives directly under the app source root (or under an optional <Module>/ grouping) — there is no top-level Features/ wrapper.
<Feature>/ ← feature root (pluralized domain noun)
├── <Feature>.tsx ← composition page
├── <ConceptName>.cs ← shared ConceptAs<T> / EventSourceId<T> types for the feature
└── <SliceName>/ ← slice (action or view name) — the invariant unit
├── <SliceName>.cs ← ALL backend artifacts in ONE file
├── <Component>.tsx ← React component
└── when_<behavior>/ ← specs
└── and_<scenario>.cs
✅ Correct:
Authors/
├── Authors.tsx
├── AuthorId.cs
├── AuthorName.cs
├── Registration/
│ ├── Registration.cs ← command + event + constraint + validator
│ ├── AddAuthor.tsx
│ └── when_registering/
│ └── and_there_are_no_authors.cs
└── Listing/
├── Listing.cs ← read model + projection + query
└── Listing.tsx
What ships with it
4 files 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.
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.
- 1mo ago First seen · 208 lines · 89 tokens per session scan A 929ed88481e2
cratis-vertical-slice is a skill published in the GitHub repository Cratis/VerticalSlices (2 stars, last pushed 1mo ago), licensed MIT. It adds 89 tokens to every session and 1,568 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to cratis-vertical-slice, differing in 4 lines, and is treated as a copy.
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