Kotlin Tooling Java To Kotlin

What it does

When your agent uses it

• Converting Java source files to idiomatic Kotlin
• User mentions java to kotlin
• Migrate java to kotlin
• Working with .java files that need to become .kt files

Example prompts

• “java to kotlin”
• “convert java”
• “migrate java to kotlin”
• “/kotlin-tooling-java-to-kotlin”

Workflow steps

5 steps, taken from the step headings in SKILL.md.

1. 1Scan & Detect Frameworks
2. 2Convert
3. 3Write Output
4. 4Preserve Git History
5. 5Verify

What it can do on your machine

Read from SKILL.md and the folder at commit e0f258b. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • git

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md. Its commands use git, which can reach the network depending on how they are called.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Kotlin Tooling Java To Kotlin loads about 1.4k tokens when it runs, and up to ~23k if it reads all its reference files. Until then it costs about 98 tokens; SKILL.md has 438 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~98

When it runs · the whole SKILL.md, loaded when a task matches

~1.4k

With references · SKILL.md plus every file in references/, read only if the agent opens them

~23k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from JetBrains/skills at commit e0f258b, republished under its Apache-2.0 licence (© JetBrains). 438 words, ~1,420 tokens.

name

kotlin-tooling-java-to-kotlin

description

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.

license

Apache-2.0

metadata.short-description

Convert Java code to idiomatic Kotlin

metadata.author

JetBrains

metadata.version

1.0.0

metadata.source

https://github.com/Kotlin/kotlin-agent-skills/tree/main/skills/kotlin-tooling-java-to-kotlin

digraph j2k_workflow {
  rankdir=TB;
  "User specifies files" -> "Step 0: Scan & Detect";
  "Step 0: Scan & Detect" -> "Load framework guides";
  "Load framework guides" -> "Step 1: Convert";
  "Step 1: Convert" -> "Step 2: Write .kt";
  "Step 2: Write .kt" -> "Step 3: Git rename";
  "Step 3: Git rename" -> "Step 4: Verify";
  "Step 4: Verify" -> "Next file?" [label="pass"];
  "Step 4: Verify" -> "Fix issues" [label="fail"];
  "Fix issues" -> "Step 1: Convert";
  "Next file?" -> "Step 0: Scan & Detect" [label="batch: yes"];
  "Next file?" -> "Done" [label="no more files"];
}

# Phase 1: Rename (creates rename tracking)
git mv src/main/java/com/example/Foo.java src/main/kotlin/com/example/Foo.kt
git commit -m "Rename Foo.java to Foo.kt"

# Phase 2: Replace content (tracked as modification, not new file)
# Write the converted Kotlin content to Foo.kt
git commit -m "Convert Foo from Java to Kotlin"

git mv src/main/java/com/example/Foo.java src/main/java/com/example/Foo.kt

© JetBrains, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 15 other files (references, assets) in kotlin-tooling-java-to-kotlin of JetBrains/skills.

• SKILL.md
• assets/checklist.md
• references/CONVERSION-METHODOLOGY.md
• references/KNOWN-ISSUES.md
• references/frameworks/DAGGER-HILT.md
• references/frameworks/GUICE.md
• references/frameworks/HIBERNATE.md
• references/frameworks/JACKSON.md
• references/frameworks/JUNIT.md
• references/frameworks/LOMBOK.md
• references/frameworks/MICRONAUT.md
• references/frameworks/MOCKITO.md
• references/frameworks/QUARKUS.md
• references/frameworks/RETROFIT.md
• references/frameworks/RXJAVA.md
• references/frameworks/SPRING.md

Open the folder on GitHubat commit e0f258b

Used in 3 other repositories

We found 3 copies of this SKILL.md (exact, near-identical or edited) in other folders, from 3 other GitHub owners. This page covers the copy in JetBrains/skills, which our catalogue first saw on October 7, 2026.

• Peakmain/BasicUI.claude/skills/kotlin-tooling-java-to-kotlin
• Kwensiu/DPIS.agents/skills/kotlin-tooling-java-to-kotlin
• Kotlin/kotlin-agent-skillsskills/kotlin-tooling-java-to-kotlin