dejared-mcp

A Model Context Protocol (MCP) server for exploring, analyzing, and decompiling Java JAR files. Designed for AI-powered development tools, dejared-mcp connects your IDE or CLI assistant to inspect package structures, search bytecode, and decompile classes using CFR, Vineflower, or Procyon.

Overview
Prerequisites
Quick Start
Features
Decompiler Engines
Installation and Configuration
Custom Java Path
Server Configuration
How It Works
FAQ and Troubleshooting
Contributing
Third-Party Licenses
License

Overview

dejared-mcp is a Java-based MCP server distributed as an npm package. It provides nine tools organized into three categories: discovery, hunting, and deep analysis. AI assistants use these tools to navigate JAR file structures, search for classes and string literals in bytecode, and decompile .class files back to readable Java source code.

The npm package acts as a thin wrapper that downloads and caches the server JAR on first run, then spawns it via java -jar using stdio transport.

Prerequisites

Node.js 18 or later
Java 17 or later (JRE is sufficient)

Quick Start

Add the following to your MCP client configuration:

{
  "mcpServers": {
    "dejared": {
      "command": "npx",
      "args": ["-y", "dejared-mcp"]
    }
  }
}

See Installation and Configuration for tool-specific instructions.

Features

Discovery

Browse and read JAR contents.

| Tool | Description | |------|-------------| | dejared_list_packages | List all packages with class counts | | dejared_list_classes | List classes in a specific package | | dejared_list_resources | List non-class resource files | | dejared_read_resource | Read text resources (YAML, XML, properties, JSON, and others) |

Hunting

Search inside JAR files.

| Tool | Description | |------|-------------| | dejared_search_class | Search classes by name | | dejared_search_string | Search string literals in bytecode (URLs, SQL, error messages) |

Deep Analysis

Inspect metadata and decompile classes.

| Tool | Description | |------|-------------| | dejared_get_metadata | Extract class metadata via ASM (fast, no decompilation) | | dejared_dump_package_metadata | Batch metadata extraction for entire packages | | dejared_decompile_class | Decompile .class files to Java source code |

Decompiler Engines

dejared-mcp supports three decompiler engines. The engine can be specified per request via the dejared_decompile_class tool.

| Engine | Description | |--------|-------------| | CFR (default) | Reliable general-purpose decompiler | | Vineflower | Modern fork of FernFlower, handles newer Java features well | | Procyon | Alternative engine, can handle some edge cases better |

Installation and Configuration

The standard configuration below works with most MCP-compatible tools. Expand the relevant section for tool-specific instructions.

{
  "mcpServers": {
    "dejared": {
      "command": "npx",
      "args": ["-y", "dejared-mcp"]
    }
  }
}

Add via the Amp VS Code extension settings screen or by updating your settings.json file:

"amp.mcpServers": {
  "dejared": {
    "command": "npx",
    "args": ["-y", "dejared-mcp"]
  }
}

Amp CLI:

amp mcp add dejared -- npx -y dejared-mcp

</details> <details> <summary>Antigravity Editor</summary>

Edit ~/.gemini/antigravity/mcp_config.json:

{
  "mcpServers": {
    "dejared": {
      "command": "npx",
      "args": ["-y", "dejared-mcp"]
    }
  }
}

Or install through the MCP Store if available.

</details> <details> <summary>Claude Code</summary>

claude mcp add dejared -- npx -y dejared-mcp

Or add it to your project's .mcp.json using the standard config above.

Plugin (Marketplace) installs both the MCP server and the /jar-analysis skill:

claude plugin marketplace add HuynhKhanh1402/dejared-mcp
claude plugin install dejared@dejared-mcp-marketplace

</details> <details> <summary>Claude Desktop</summary>

Edit the Claude Desktop config file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json

Add the standard config above and restart Claude Desktop.

</details> <details> <summary>Cline</summary>

Add the standard config above to your MCP settings file.

</details> <details> <summary>Codex</summary>

codex mcp add dejared npx "-y dejared-mcp"

Or edit ~/.codex/config.toml:

[mcp_servers.dejared]
command = "npx"
args = ["-y", "dejared-mcp"]

</details> <details> <summary>Copilot CLI</summary>

Interactive:

/mcp add

Then fill in:

Server Name: dejared
Server Type: STDIO
Command: npx -y dejared-mcp

Or edit ~/.copilot/mcp-config.json:

{
  "mcpServers": {
    "dejared": {
      "type": "local",
      "command": "npx",
      "args": ["-y", "dejared-mcp"],
      "tools": ["*"]
    }
  }
}

</details> <details> <summary>Cursor</summary>

Create or edit .cursor/mcp.json in your project root (project-level) or ~/.cursor/mcp.json (global) using the standard config above.

</details> <details> <summary>Gemini CLI</summary>

gemini mcp add dejared npx -y dejared-mcp

Or edit ~/.gemini/settings.json (global) or .gemini/settings.json (project) using the standard config above.

Use /mcp in a Gemini CLI session to verify the server is connected.

</details> <details> <summary>Goose</summary>

Go to Advanced settings > Extensions > Add custom extension. Name to your liking, use type STDIO, and set the command to npx -y dejared-mcp.

</details> <details> <summary>JetBrains IDEs</summary>

Go to Settings > Tools > AI Assistant > Model Context Protocol (MCP).

Click + Add and configure:

Name: dejared
Transport: Stdio
Command: npx
Arguments: -y dejared-mcp

</details> <details> <summary>Kiro</summary>

Create or edit .kiro/settings/mcp.json using the standard config above.

</details> <details> <summary>opencode</summary>

Edit ~/.config/opencode/opencode.json:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "dejared": {
      "type": "local",
      "command": ["npx", "-y", "dejared-mcp"],
      "enabled": true
    }
  }
}

</details> <details> <summary>Qodo Gen</summary>

Open Qodo Gen chat panel in VS Code or IntelliJ > Connect more tools > + Add new MCP > Paste the standard config above > Save.

</details> <details> <summary>VS Code (GitHub Copilot)</summary>

Create or edit .vscode/mcp.json in your project root:

{
  "servers": {
    "dejared": {
      "command": "npx",
      "args": ["-y", "dejared-mcp"]
    }
  }
}

After saving, click the Start button that appears in the MCP config file, then use Agent mode in Copilot Chat.

</details> <details> <summary>Windsurf</summary>

Open Windsurf settings, navigate to MCP servers, and add a new server using the command type with npx -y dejared-mcp. Or add the standard config under mcpServers in your settings.

</details> <details> <summary>Pure Java (no Node.js required)</summary>

If you prefer to run the server JAR directly without Node.js:

Download the latest JAR from GitHub Releases.
Run it:
```
java -jar dejared-mcp-0.2.0.jar
```

Configure your MCP client to use the JAR directly instead of npx:

{
  "mcpServers": {
    "dejared": {
      "command": "java",
      "args": ["-jar", "/path/to/dejared-mcp-0.2.0.jar"]
    }
  }
}

</details>

Custom Java Path

If Java is not in your system PATH, set the DEJARED_JAVA_PATH environment variable in your MCP config. This applies to all npx-based configurations:

{
  "mcpServers": {
    "dejared": {
      "command": "npx",
      "args": ["-y", "dejared-mcp"],
      "env": {
        "DEJARED_JAVA_PATH": "/path/to/java"
      }
    }
  }
}

Server Configuration

| Property | Default | Description | |----------|---------|-------------| | dejared.cache.max-size | 500 | Max entries in the decompilation LRU cache | | dejared.security.max-resource-size | 5242880 | Max resource file size (bytes) | | dejared.security.decompile-timeout-seconds | 30 | Timeout per decompilation |

How It Works

The npm package is a thin Node.js wrapper. On first run it:

Checks the platform cache directory for a cached JAR matching the current version.
- Linux: $XDG_CACHE_HOME/dejared-mcp (defaults to ~/.cache/dejared-mcp)
- macOS: ~/Library/Caches/dejared-mcp
- Windows: %LOCALAPPDATA%\dejared-mcp
Downloads the JAR from GitHub Releases if not cached

Dejared MCP

Install / Use

README