Recaf MCP Plugin

Gradle-based Recaf 4.x plugin that starts a local MCP (Model Context Protocol) server.

The server exposes a small set of tools to inspect/modify the currently open Recaf workspace (list classes, decompile, disassemble, assemble+apply, mappings).

Requirements

• Recaf 4.x
• Java 22+ (this project uses a Gradle toolchain set to Java 22)

Building

Build the plugin jar:

./gradlew build

This generates build/libs/example-plugin-{VERSION}.jar.

Installing Into Recaf

1. Locate Recaf's plugins directory:
   • Windows: %APPDATA%\Recaf\plugins
   • Linux: $HOME/Recaf/plugins
2. Copy the jar from build/libs/ into that folder.
3. Start Recaf and check the logs for MCP startup messages.

Running Recaf From This Project

This project includes a runRecaf task that builds the plugin and launches Recaf with build/libs registered as a plugin directory.

./gradlew runRecaf

Plugin Info

• The plugin entry point class is src/main/java/org/example/plugin/RecafMcpPlugin.java.
• The service entry is generated from build.gradle (pluginMainClass).

MCP Transport

• Protocol: JSON-RPC 2.0 over HTTP POST
• Bind: loopback only (127.0.0.1)
• Endpoint: http://127.0.0.1:33333/mcp
• Auth: none (local only)

Recaf GUI Panel

The plugin creates a Recaf MCP dockable in the bottom area.

• Shows endpoint with copy button
• Shows total calls and error count
• Shows latest obfuscation, malware, and mapping summaries
• Shows recent tool calls with durations
• Recent calls width is user-resizable
• Logging tab remains the default selected tab on startup

Tool Catalog

All class names use JVM internal format (com/example/Foo).

Workspace And Class Introspection

• recaf_workspace_status
• recaf_workspace_list_classes
• recaf_workspace_list_files
• recaf_class_get_outline
• recaf_class_info
• recaf_file_read

Code View And Edit

• recaf_class_decompile (supports decompiler, optional single-method isolation with methodName + methodDesc)
• recaf_class_disassemble
• recaf_method_disassemble
• recaf_method_bytecode (JASM text)
• recaf_class_assemble_apply

Mapping

• recaf_mapping_apply (explicit renames you provide)
• recaf_mapping_generate (auto-generate renames for likely obfuscated/random names)

Mapping tools return rename counts and change lists (from -> to) so MCP clients can show exactly what changed.

Search And Graph Analysis

• recaf_search_string
• recaf_search_number
• recaf_search_references
• recaf_search_declarations
• recaf_method_callgraph
• recaf_class_inheritance

Comments

• recaf_comment_get
• recaf_comment_set

Security / Obfuscation Heuristics

• recaf_check_obfuscation
• recaf_check_malware

recaf_check_malware reports category plus exact detection location (className, method, match type, matched API/constant).

UI Navigation

• recaf_ui_open_class
• recaf_ui_open_file

Quick Test (curl)

Initialize:

curl -s -X POST "http://127.0.0.1:33333/mcp" \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{}}'

List tools:

curl -s -X POST "http://127.0.0.1:33333/mcp" \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","id":2,"method":"tools/list","params":{}}'

Call a tool (example: list classes):

curl -s -X POST "http://127.0.0.1:33333/mcp" \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"recaf_workspace_list_classes","arguments":{"prefix":"com/example/","limit":50}}}'

Call a tool (example: decompile):

curl -s -X POST "http://127.0.0.1:33333/mcp" \
  -H "Content-Type: application/json" \
  --data '{"jsonrpc":"2.0","id":4,"method":"tools/call","params":{"name":"recaf_class_decompile","arguments":{"internalName":"com/example/Foo","timeout":5000}}}'

Showcase

https://github.com/user-attachments/assets/e9de7c4d-b956-4424-bbff-19b1d0d69afe

https://github.com/user-attachments/assets/ce12f257-66ce-4e93-92de-3dace355d2ed

Recaf Plugin Dev Docs

Recaf developer documentation: https://recaf.coley.software/dev/index.html