Borrowing it
Nothing to install: this file belongs to costular/Minitask. 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/costular/Minitask/main/.agents/skills/kotlin-types-value-class/SKILL.mdgit clone --depth 1 https://github.com/costular/MinitaskWrote 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/costular/minitask/kotlin-types-value-class)<a href="https://agentmods.dev/skills/costular/minitask/kotlin-types-value-class"><img src="https://agentmods.dev/badge/skills/costular/minitask/kotlin-types-value-class/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/costular/minitask/kotlin-types-value-class"><img src="https://agentmods.dev/badge/skills/costular/minitask/kotlin-types-value-class.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 | $0.00032 | $0.01628 |
| Opus 5.5 | $0.00013 | $0.00651 |
| Sonnet 5.5 | $0.00006 | $0.00326 |
| Haiku 4.5 | $0.00003 | $0.00163 |
Grade A, and why
kotlin-types-value-class 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
97% identical to kotlin-types-value-class — 2 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 — 120 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Kotlin value class vs data class
Core principle
Prefer @JvmInline value class for single-field types that carry domain meaning. Data classes are for aggregating multiple fields. A value class gives you type safety (you can't mix up UserId and String) without the allocation overhead of a data class.
When to use this skill
- Writing a new Kotlin type that wraps a single value
- Reviewing a data class that has only one property
- Seeing primitive types (
String,Long,Int, etc.) used where a domain type would prevent misuse - Compose compiler reports showing unstable parameters that could be value classes
Decision flow
| Situation | Prefer |
|---|---|
Single field + domain-meaningful (UserId, EmailAddress, Percentage) |
@JvmInline value class |
| Single field + no domain meaning (just grouping) | Type alias or keep the primitive |
| Multiple fields | Data class |
Needs custom equals/hashCode/toString beyond the wrapped value |
Data class (value classes delegate to the underlying type) |
| Used as a generic type argument or nullable in hot paths | Data class or primitive (autoboxing cost) |
// GOOD: domain-meaningful single field
@JvmInline value class UserId(val value: String)
@JvmInline value class EmailAddress(val value: String)
@JvmInline value class Percentage(val value: Float)
// BAD: data class wrapping a single field
data class UserId(val value: String) // unnecessary allocation
data class EmailAddress(val value: String) // type safety without the overhead is available
// BAD: value class with no domain meaning
@JvmInline value class Wrapper(val value: String) // just use the String, or a type alias
// BAD: value class needing custom equality
@JvmInline value class CaseInsensitiveString(val value: String)
// value class equals delegates to String equals, which IS case-sensitive
// Use a data class if you need different equality semantics
Compose stability
@JvmInline value class is treated as Stable by the Compose compiler when its underlying type is stable (primitives, String, and other stable types). This means:
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 · 120 lines · 32 tokens per session scan A 34fad91768a9
kotlin-types-value-class is a skill published in the GitHub repository costular/Minitask (12 stars, last pushed 6d ago), licensed Apache-2.0. It adds 32 tokens to every session and 1,628 once invoked, about $0.0001 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 97% identical to kotlin-types-value-class, differing in 2 lines, and is treated as a copy.
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