Amethyst is an Android client for Nostr, a social network protocol that lets people control their own social activity and connections. People use it to read and publish Nostr content, follow accounts, and exchange encrypted direct messages from Android and other supported platforms. The catalogue add-ons support workflows for developing or operating the client.
Borrowing it
Nothing to install: this file belongs to vitorpamplona/amethyst. 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/vitorpamplona/amethyst/main/.claude/skills/kotlin-types-value-class/SKILL.mdgit clone --depth 1 https://github.com/vitorpamplona/amethystWrote 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/vitorpamplona/amethyst/kotlin-types-value-class)<a href="https://agentmods.dev/skills/vitorpamplona/amethyst/kotlin-types-value-class"><img src="https://agentmods.dev/badge/skills/vitorpamplona/amethyst/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/vitorpamplona/amethyst/kotlin-types-value-class"><img src="https://agentmods.dev/badge/skills/vitorpamplona/amethyst/kotlin-types-value-class.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 | $0.00045 | $0.01641 |
| Opus 5 | $0.00023 | $0.00821 |
| Sonnet 5 | $0.00009 | $0.00328 |
| Haiku 4.5 | $0.00005 | $0.00164 |
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 10d 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- kotlin-types-value-class — 97% identical, 2 lines differ
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.
- 10d ago First seen · 120 lines · 45 tokens per session scan A 6b9023bef264
kotlin-types-value-class is a skill published in the GitHub repository vitorpamplona/amethyst (1,597 stars, last pushed today), licensed MIT. It adds 45 tokens to every session and 1,641 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 2026-08-30.
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