kotlin-specialist

kotlin-specialist is a skill for Claude Code, Codex from johnefemer/skillfish. It costs 0 tokens per session (5,715 once invoked), scanned A, original, no licence file.

A guide to developing applications in Kotlin, a programming language used for Android, server, and multiplatform software.

In plain words
What is it for?
Use it with coroutines, flows, Jetpack Compose, Kotlin Multiplatform, Spring Boot, testing, and Java migration.
Why use it?
It helps developers work with Kotlin concurrency, data streams, user interfaces, testing, and migration from Java.

Skill for Claude CodeCodex

Which agent this was written for is unclear — body not stored (licence); the path alone says nothing.

Good fit Use it with coroutines, flows, Jetpack Compose, Kotlin Multiplatform, Spring Boot, testing, and Java migration.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/johnefemer/skillfish/kotlin-specialist
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add johnefemer/skillfish --skill kotlin-specialist
Clone the repo
git clone --depth 1 https://github.com/johnefemer/skillfish

Made for: Claude Code, Codex.

Wrote 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.

agentmods badge for kotlin-specialist

README.md
[![agentmods](https://agentmods.dev/badge/skills/johnefemer/skillfish/kotlin-specialist/github.svg)](https://agentmods.dev/skills/johnefemer/skillfish/kotlin-specialist)
Your own site
<a href="https://agentmods.dev/skills/johnefemer/skillfish/kotlin-specialist"><img src="https://agentmods.dev/badge/skills/johnefemer/skillfish/kotlin-specialist/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.

agentmods 80×15 button for kotlin-specialist

Your own site · 80×15
<a href="https://agentmods.dev/skills/johnefemer/skillfish/kotlin-specialist"><img src="https://agentmods.dev/badge/skills/johnefemer/skillfish/kotlin-specialist.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,715 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. A grade says what 26 rules found in the file — not that it is safe.
Origin unknown 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 $0.00000 $0.05715
Opus 5.5 $0.00000 $0.02286
Sonnet 5.5 $0.00000 $0.01143
Haiku 4.5 $0.00000 $0.00571

Measured 2mo ago against content hash f69b7bba4fd4, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

kotlin-specialist scanned grade A with 1 finding 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.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

fun fetch(path: String, headers: Map<String, String> = emptyMap()): Response { ... }
skills/kotlin-specialist/SKILL.md · 824 lines

The source is not reproduced here

No licence file

A repository with no LICENSE is all rights reserved by default, so the body is not copied here. The metadata, the measurements and the link are.

Read it on GitHub

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. 2mo ago First seen · 824 lines · 0 tokens per session scan A f69b7bba4fd4

Subscribe to this mod's changes

kotlin-specialist is a skill published in the GitHub repository johnefemer/skillfish (4 stars, last pushed 4d ago), with no licence file. It costs nothing until one of its globs matches a file; then it loads 5,715 tokens. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.

Related

kotlin-specialist compared with skills from other repositories

kotlin-specialist next to 6 skills from other repositories
ModTypeStarsLast pushLicenceScanTokensWorks with
kotlin-specialistjohnefemer/skillfishSkill44d agononeA0Claude Code, Codex
wear-compose-m3android/skillsSkill10kyesterdayApache-2.0A91Claude Code
ink-custom-brush-builderandroid/skillsSkill10kyesterdayApache-2.0A159Claude Code
kotlin-specialistJeffallan/claude-skillsSkill12k7d agoMITA86Claude Code
swiftui-devOrkas-AI/OrkasSkill9.0kyesterdayMITA3Claude Code, Codex
build-android-binarymicrosoft/power-platform-skillsSkill1.1kyesterdayMITA150Claude Code
kotlin-androidericrisco/rsc-harnessSkill5032d agoMITA78Claude Code, Codex