Borrowing it
Nothing to install: this file belongs to moeru-ai/auv. 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/moeru-ai/auv/main/.agents/skills/m05-type-driven/SKILL.mdgit clone --depth 1 https://github.com/moeru-ai/auvWrote 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/moeru-ai/auv/m05-type-driven)<a href="https://agentmods.dev/skills/moeru-ai/auv/m05-type-driven"><img src="https://agentmods.dev/badge/skills/moeru-ai/auv/m05-type-driven/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/moeru-ai/auv/m05-type-driven"><img src="https://agentmods.dev/badge/skills/moeru-ai/auv/m05-type-driven.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00060 | $0.01040 |
| Opus 5.5 | $0.00024 | $0.00416 |
| Sonnet 5.5 | $0.00012 | $0.00208 |
| Haiku 4.5 | $0.00006 | $0.00104 |
Grade A, and why
m05-type-driven 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 2mo 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.
How it starts
The opening of the file, as written. The whole thing — 176 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Type-Driven Design
Layer 1: Language Mechanics
Core Question
How can the type system prevent invalid states?
Before reaching for runtime checks:
- Can the compiler catch this error?
- Can invalid states be unrepresentable?
- Can the type encode the invariant?
Error → Design Question
| Pattern | Don't Just Say | Ask Instead |
|---|---|---|
| Primitive obsession | "It's just a string" | What does this value represent? |
| Boolean flags | "Add an is_valid flag" | Can states be types? |
| Optional everywhere | "Check for None" | Is absence really possible? |
| Validation at runtime | "Return Err if invalid" | Can we validate at construction? |
Thinking Prompt
Before adding runtime validation:
-
Can the type encode the constraint?
- Numeric range → bounded types or newtypes
- Valid states → type state pattern
- Semantic meaning → newtype
-
When is validation possible?
- At construction → validated newtype
- At state transition → type state
- Only at runtime → Result with clear error
-
Who needs to know the invariant?
- Compiler → type-level encoding
- API users → clear type signatures
- Runtime only → documentation
Trace Up ↑
When type design is unclear:
"Need to validate email format"
↑ Ask: Is this a domain value object?
↑ Check: m09-domain (Email as Value Object)
↑ Check: domain-* (validation requirements)
| Situation | Trace To | Question |
|---|---|---|
| What types to create | m09-domain | What's the domain model? |
| State machine design | m09-domain | What are valid transitions? |
| Marker trait usage | m04-zero-cost | Static or dynamic dispatch? |
Trace Down ↓
From design to implementation:
"Need type-safe wrapper for primitives"
↓ Newtype: struct UserId(u64);
"Need compile-time state validation"
↓ Type State: Connection<Connected>
"Need to track phantom type parameters"
↓ PhantomData: PhantomData<T>
"Need capability markers"
↓ Marker Trait: trait Validated {}
"Need gradual construction"
↓ Builder: Builder::new().field(x).build()
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.
- 2mo ago First seen · 176 lines · 60 tokens per session scan A 56895dac5c47
m05-type-driven is a skill published in the GitHub repository moeru-ai/auv (203 stars, last pushed 2d ago), licensed Apache-2.0. It adds 60 tokens to every session and 1,040 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-08-30.
m05-type-driven compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| m05-type-drivenmoeru-ai/auv | Skill | 203 | 2d ago | Apache-2.0 | A | 60 | Claude Code |
| rust-patternsaffaan-m/ECC | Skill | 298k | 4d ago | MIT | A | 28 | Claude Code, Kiro |
| update-v8-versionopeninterpreter/openinterpreter | Skill | 69k | 2d ago | Apache-2.0 | A | 86 | Codex |
| dd-code-generationDataDog/pup | Skill | 1.0k | yesterday | Apache-2.0 | A | 16 | Claude Code |
| omh-rustrlaope/oh-my-hermes | Skill | 5.2k | today | MIT | A | 74 | Claude Code, Codex |
| swiftidebosun-ai/swiftide | Skill | 802 | yesterday | MIT | A | 47 | Claude Code, Codex |
| azure-keyvault-secrets-rustbenjaminasterA/antigravity-awesome-skills | Skill | 461 | yesterday | MIT | A | 0 | Claude Code, Codex |