mcp-jpexs

MCP (Model Context Protocol) server for decompiling Adobe Flash SWF files with JPEXS FFDec. Lets AI agents extract resources and decompile ActionScript directly from a chat session.

Requirements

• Node.js 18+
• Java 8 on the PATH — FFDec (the bundled decompiler) does not run on newer Java versions. The server detects incompatible Java versions and returns a clear error message.

Installation

Published on npm as mcp-jpexs. No install needed for MCP clients — npx fetches it automatically (see below). For local development:

git clone https://github.com/marcuth/mcp-jpexs.git
cd mcp-jpexs
npm install
npm run build

Usage

Register the server in your MCP client:

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

Or, if you installed it globally (npm install -g mcp-jpexs):

{
    "mcpServers": {
        "jpexs": {
            "command": "mcp-jpexs"
        }
    }
}

Running from a local clone also works:

{
    "mcpServers": {
        "jpexs": {
            "command": "node",
            "args": ["D:/path/to/mcp-jpexs/dist/index.js"]
        }
    }
}

The server communicates over stdio.

Tools

extract_swf_resources

Extracts resources from a SWF file to a directory and returns the list of generated files.

| Param | Type | Required | Description | | ----------- | ---------- | -------- | ------------------------------------------------------------------------ | | file | string | yes | Path to the source .swf file | | outputDir | string | no | Output directory (created if missing). Defaults to a temporary directory | | items | string[] | no | Resource types to export. Defaults to ["all"] | | formats | string[] | no | Output formats, e.g. script:as, image:png. Omit for defaults |

Items: all, fla, text, script, image, shape, movie, font, frame, sprite, button, sound, binaryData, morphshape

Formats:

| Category | Options | | ---------- | --------------------------------------------------------------------------------------------------- | | Script | script:as, script:hex, script:pcode, script:pcodehex | | Shape | shape:svg, shape:bmp, shape:png, shape:canvas | | MorphShape | morphshape:svg, morphshape:canvas | | Frame | frame:bmp, frame:png, frame:svg, frame:gif, frame:avi, frame:pdf, frame:canvas | | Sprite | sprite:bmp, sprite:png, sprite:svg, sprite:gif, sprite:avi, sprite:pdf, sprite:canvas | | Button | button:bmp, button:png, button:svg | | Image | image:bmp, image:png, image:svg, image:jpeg, image:png_gif_jpeg | | Text | text:svg, text:plain, text:formatted | | Font | font:ttf, font:woff | | Sound | sound:flv, sound:wav, sound:mp3_wav_flv |

decompile_swf_scripts

Decompiles ActionScript from a SWF and returns the script contents inline — useful for analyzing SWF logic without reading files from disk.

| Param | Type | Required | Description | | -------- | -------- | -------- | ---------------------------------------------------------------------- | | file | string | yes | Path to the source .swf file | | format | string | no | script:as (default), script:hex, script:pcode, script:pcodehex |

Large results are truncated (at most 200 files / 100,000 characters total).

Development

npm run build         # compile TypeScript to dist/
npm run start         # run the server
npm run watch         # tsc in watch mode
npm run lint          # eslint
npm run lint:fix      # eslint --fix (removes unused imports)
npm run format        # prettier --write
npm run format:check  # prettier --check

Code style

• Prettier: no semicolons, double quotes, 4-space indent, sorted/grouped imports (@ianvs/prettier-plugin-sort-imports)
• ESLint: flat config with typescript-eslint + eslint-plugin-unused-imports (unused imports are removed by lint:fix)

TypeScript

Builds use the native TypeScript 7 compiler (aliased as @typescript/native, providing tsc). The typescript package is aliased to @typescript/typescript6 because typescript-eslint still depends on the TS 6 API — see the TypeScript 7.0 announcement.

License

MIT