File Writer MCP Server

A Node.js implementation of the Model Context Protocol (MCP) designed for seamless file operations within LM Studio and other MCP-compatible environments. This server provides a robust interface for large language models to create, append, and manage files in multiple formats including Plain Text, Markdown, CSV, and Microsoft Excel (XLSX).

Features

• Multi-Format Support: Handles data transformation for .txt, .md, .csv, and .xlsx files.

• Structured Data Processing: Accepts table data as JSON objects and converts them into the requested format automatically.

• Flexible Write Modes:

  • Append (Default): Adds new data to the end of existing files.

  • Overwrite: Replaces existing files with new content.

  • Numbered Backup: Preserves existing data by creating incremented versions (e.g., file.1.csv).

• Security Focused: Restricts all file operations to a user-specified root directory to prevent unauthorized path traversal.

• Excel Integration: Utilizes ExcelJS for high-fidelity generation of binary spreadsheet files.

Installation

Prerequisites

• Node.js (v18 or higher)

• npm

Setup

1. Clone the repository or copy the source files to your local machine.

2. Install the required dependencies:

   npm install

3. Build the project:

   npm run build

Configuration for LM Studio

To use this server in LM Studio, add it to your MCP settings with the following configuration:

{
  "mcpServers": {
    "file-writer": {
      "command": "node",
      "args": [
        "C:/Users/szpon/file_writer_mcp/dist/index.js",
        "--root",
        "C:/your/default/directory"
      ]
    }
  }
}

Arguments

• --root <path>: (Required) The absolute path to the default directory for relative file operations.

• --overwrite: (Optional/Legacy) Provided for compatibility with older configs; ignored in favor of tool selection.

• --backup: (Optional/Legacy) Provided for compatibility with older configs; ignored in favor of tool selection.

Tool Usage

The server provides three distinct tools to give you clear control over file handling directly from the LM Studio sidebar:

1. write_file: Use this for standard operations. It appends data to existing files or creates them if they do not exist.

2. write_file_overwrite: Use this to completely replace an existing file with new data.

3. write_file_backup: Use this to save data while preserving the original. If the file exists, it creates a numbered backup (e.g., data.1.csv).

Tool Arguments

• path (string): The filename or full absolute path. If a relative path is provided, it resolves against the --root directory. If an absolute path is provided, the server writes directly to that location.

• format (string): The desired file extension (txt, md, csv, or xlsx).

• data (object):

  • headers (string[]): Column names for table formats.

  • rows (any[][]): The dataset to be written.

  • content (string, optional): Plain text content for .txt files.

Development

Running Tests

The project uses Vitest for unit testing. To execute the test suite:

npm test

Building

To compile the TypeScript source into the distribution directory:

npm run build

License

This project is provided as-is for integration with LM Studio and other MCP clients.