Ffdecmcp

MCP (Model Context Protocol) wrapper for JPEXS Free Flash Decompiler (FFDec) - expose SWF decompilation and analysis tools to AI assistants like Claude.

Tools

1. decompile_swf

Decompile all ActionScript code from a SWF file to organized directory structure.

Parameters:

• swf_path (required): Absolute path to SWF file
• output_dir (required): Directory for decompiled scripts
• timeout (optional): Timeout in seconds (default: 60)

2. extract_actionscript

Extract specific ActionScript classes by name (AS3 only). Faster than full decompilation when you only need specific classes.

Parameters:

• swf_path (required): Absolute path to SWF file
• class_names (required): List of class names (e.g., ['com.example.Main'])
• output_dir (required): Directory for extracted classes
• timeout (optional): Timeout in seconds (default: 60)

3. list_symbols

List all ActionScript classes and symbols in a SWF file. Great for exploring a SWF before full decompilation.

Parameters:

• swf_path (required): Absolute path to SWF file

Returns: Structured JSON with packages, classes, and total count

4. extract_assets

Extract images, sounds, fonts, shapes, movie clips, and binary data from SWF.

Parameters:

• swf_path (required): Absolute path to SWF file
• output_dir (required): Directory for extracted assets
• asset_types (optional): Types to extract - image, sound, font, shape, movie, binaryData, all (default: ["all"])
• timeout (optional): Timeout in seconds (default: 60)

5. get_swf_metadata

Extract SWF header information (dimensions, frame rate, compression, etc.). Fast and doesn't require decompilation.

Parameters:

• swf_path (required): Absolute path to SWF file

Returns: JSON with version, width, height, frame_rate, frame_count, compression

6. deobfuscate

Run FFDec's deobfuscation algorithms to remove obfuscation and anti-decompilation tricks.

Parameters:

• swf_path (required): Absolute path to obfuscated SWF
• output_path (required): Path for deobfuscated SWF
• level (optional): Deobfuscation level - traps, deadcode, max (default: max)
• timeout (optional): Timeout in seconds (default: 60)

Quick Start

Prerequisites: Python 3.10+ and Java (for running the FFDec JAR).

Claude Code

claude mcp add ffdecmcp -- uvx ffdecmcp

That's it. On first run, FFDec will be auto-downloaded if not already installed.

Claude Desktop

Add to your config file (~/Library/Application Support/Claude/claude_desktop_config.json on macOS, %APPDATA%\Claude\claude_desktop_config.json on Windows):

{
  "mcpServers": {
    "ffdecmcp": {
      "command": "uvx",
      "args": ["ffdecmcp"]
    }
  }
}

Standalone

# Just run it - FFDec will be auto-downloaded to ~/.ffdecmcp/ if needed
uvx ffdecmcp

# Or point to an existing FFDec installation
uvx ffdecmcp --ffdec-path /path/to/ffdec.jar

Installation

No installation is required when using uvx. For a permanent install:

uv pip install ffdecmcp
# or
pip install ffdecmcp

FFDec

FFDec is automatically downloaded on first run if not found. You can also install it manually.

The server finds FFDec in this order:

1. --ffdec-path CLI arg / FFDEC_PATH env var
2. Previously auto-downloaded JAR (~/.ffdecmcp/ffdec.jar)
3. Common install locations and PATH
4. Auto-download from GitHub

CLI Options

ffdecmcp [--ffdec-path PATH] [--timeout SECONDS]

Option	Env Var	Description
--ffdec-path	FFDEC_PATH	Path to FFDec (JAR, native binary, or WSL path)
--timeout	FFDEC_TIMEOUT	Default timeout in seconds (default: 60)

CLI arguments take precedence over environment variables.

Development

git clone https://github.com/sublimnl/ffdecmcp.git
cd ffdecmcp
uv pip install -e ".[dev]"

Example Usage in Claude

You: Can you analyze this SWF file for me?
Path: C:\Users\foo\game.swf

Claude will:
1. Use get_swf_metadata to check dimensions, version, etc.
2. Use list_symbols to see what classes are present
3. Use decompile_swf to extract all ActionScript code
4. Analyze the decompiled code and provide insights

References

• FFDec: https://github.com/jindrapetrik/jpexs-decompiler
• FFDec CLI Docs: https://github.com/jindrapetrik/jpexs-decompiler/wiki/Commandline-arguments
• Model Context Protocol: https://modelcontextprotocol.io
• FastMCP: https://github.com/jlowin/fastmcp

License

MIT License - see LICENSE file for details

Contributing

Contributions welcome! Please open an issue or PR on GitHub.