# Kotlin Tooling Java To Kotlin (agent skill)

> Kotlin Tooling Java To Kotlin is an agent skill (a SKILL.md file) from Kotlin/kotlin-agent-skills. Agents load it when converting Java source files to idiomatic Kotlin, when user mentions "java to kotlin", "j2k", "convert java", "migrate java to kotlin", or… It works with Claude Code and Codex and has 1,071 GitHub stars across a repository of 2 listed skills.

Use when converting Java source files to idiomatic Kotlin, when user mentions "java to kotlin", "j2k", "convert java", "migrate java to kotlin", or when working with .java files that need to become .kt files. Handles framework-aware conversion for Spring, Lombok, Hibernate, Jackson, Micronaut, Quarkus, Dagger/Hilt, RxJava, JUnit, Guice, Retrofit, and Mockito. Convert Java source files to idiomatic Kotlin using a disciplined 4-step conversion methodology with 5 invariants checked at each step.

## Key facts

| Fact | Value |
|---|---|
| Repository | https://github.com/Kotlin/kotlin-agent-skills |
| Skill path | skills/kotlin-tooling-java-to-kotlin/SKILL.md |
| Skill name | kotlin-tooling-java-to-kotlin |
| GitHub stars | 1,071 |
| Installs on skills.sh | not listed |
| License | Apache-2.0 |
| Skills in repo | 2 |
| Plugin marketplace | Kotlin |
| Official | yes |
| Works with | Claude Code, Codex |
| Category | Coding |
| Last commit | Sep 11, 2026 |

## When it triggers

- Use when converting Java source files to idiomatic Kotlin, when user mentions "java to kotlin", "j2k", "convert java", "migrate java to kotlin", or when working with .
- "java to kotlin"
- "j2k"
- "convert java"
- "migrate java to kotlin"

## Add this skill

### Claude Code

```sh
/plugin marketplace add Kotlin/kotlin-agent-skills
/plugin install kotlin-agent-skills@Kotlin
```

In the Claude apps, zip the skill folder and upload it under Customize > Skills > + > Upload a skill (code execution must be on).

### ChatGPT / Codex

```sh
git clone --depth 1 https://github.com/Kotlin/kotlin-agent-skills.git
cp -r kotlin-agent-skills/skills/kotlin-tooling-java-to-kotlin .agents/skills/kotlin-tooling-java-to-kotlin   # repo; ~/.agents/skills for all projects
```

### Cursor

```sh
git clone --depth 1 https://github.com/Kotlin/kotlin-agent-skills.git
cp -r kotlin-agent-skills/skills/kotlin-tooling-java-to-kotlin .cursor/skills/kotlin-tooling-java-to-kotlin   # project; ~/.cursor/skills for all projects
```

Sources (checked 2026-10-07): https://code.claude.com/docs/en/skills, https://support.claude.com/en/articles/12512180-using-skills-in-claude, https://learn.chatgpt.com/docs/build-skills, https://cursor.com/docs/context/skills

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Canonical page: https://appsgit.com/skills/kotlin-tooling-java-to-kotlin
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