Fsext Server

Overview

A high-performance, secure, and production-grade Model Context Protocol (MCP) server built with TypeScript, providing comprehensive filesystem operations, advanced text search & replace, image processing, and Tesseract OCR capabilities. Designed for LLM agent integration, it delivers strict input validation, standardized response structures, streaming large-file processing, and multi-transport remote deployment support.

This server fully complies with the official MCP specification, supportingstdio local integration, SSE legacy streaming transport, and modern Streamable HTTP bidirectional transport, serving as a universal filesystem tool backend for AI agents and automated workflow systems.

Core Features

• Full Filesystem CRUD & Directory Management：Complete file/directory creation, deletion, copy, move, metadata query, and existence verification. Supports recursive full-directory tree replication and safe move operations with conflict protection.

• Streaming File I/O for Large Files：Implements segmented text reading, chunked binary streaming reading, text/binary overwriting and appending. Avoids full memory loading, perfectly supporting GB-level large file processing.

• Advanced Text Search & In-Place Replace：Directory-wide recursive content search, single/multi-file contextual matching with preview lines, regular expression support, case-insensitive matching, and precise in-file text replacement with change statistics.

• Professional Image Processing Suite：Built-in high-performance image resize (aspect ratio lock support), precise crop, and arbitrary-angle rotation based on Sharp, covering mainstream image editing scenarios.

• Cross-Platform Tesseract OCR：WASM-first OCR recognition with customizable local Tesseract binary and tessdata paths, supporting multi-language text extraction from images without local engine installation dependency.

• Strict Strict Input Validation & Standardized Response：All tool schemas enable strict additional property prohibition, with unified success/error response structures for consistent client parsing and error handling.

• Multi-Standard MCP Transports：Natively supports three official MCP transports: stdio (local client), SSE (legacy remote stream), Streamable HTTP (modern bidirectional remote transport).

• Full TypeScript Type Safety：Complete type definitions for all tool parameters, response structures, and transport configurations, ensuring runtime stability and development friendliness.

Quick Start

Prerequisites

Node.js >=22.0.0 <27.0.0

Installation

Global Installation (Recommended for CLI Usage)

npm install -g fsext-mcp-server

Local Project Installation

npm install fsext-mcp-server

Startup Commands

1. Default Stdio Mode (For Claude Desktop / Cursor / Local MCP Clients)

# Default stdio transport for local agent integration
fsext-mcp-server-ts
fsext-mcp-server

# Short alias
fsext-ts
fsext

2. SSE Remote Transport Mode

fsext-mcp-server --transport sse --host 0.0.0.0 --port 8000

Endpoints:

• SSE Stream Subscription:http://<host>:<port>/sse

• Client Request Channel: http://<host>:<port>/messages

3. Modern Streamable HTTP Transport Mode

fsext-mcp-server --transport http --host 0.0.0.0 --port 8000

Unified Bidirectional Endpoint: http://<host>:<port>/mcp

Transport Mode Comparison

Feature	SSE Transport	Streamable HTTP
Endpoint Architecture	Dual endpoints (GET stream + POST message)	Single unified bidirectional endpoint
Communication Mode	Unidirectional server-to-client streaming	Full bidirectional streaming & standard HTTP response
Connection Stability	Prone to session inconsistency	Auto session recovery, high concurrency optimized
Specification Status	Legacy compatible	Latest official MCP standard

Client Configuration Example

MCP Client JSON Config (Cursor / Claude Desktop)

{
  "mcpServers": {
    "fsext": {
      "command": "fsext-mcp-server",
      "args": [],
      "env": {}
    }
  }
}

Unified Global Response Specification

All MCP tools adopt a consistent top-level response structure for both success and failure scenarios, enabling universal client parsing logic.

General Structure

{
  "res": {
    "success": boolean,
    "info": object
  }
}

Success Response

success: true - The info field carries tool-specific business data.

Error Response (Unified Standard)

success: false - All errors (IO failure, invalid params, path error, runtime exception) return fixed error structure:

{
  "res": {
    "success": false,
    "info": {
      "code": "ERROR_CODE",
      "message": "Human-readable detailed error message"
    }
  }
}

Full MCP Tools Reference

All tools enable additionalProperties: false strict validation to reject illegal input parameters, ensuring invocation safety.

1. Directory Operation Tools

fs_list_directory

Description: Scan target directory, return filtered absolute path list, support recursive traversal, pure file filtering, and suffix filtering.

Parameters:

• source_dir (string, required): Target directory path for scanning

• recursive (boolean, required): Enable recursive subdirectory scanning

• only_files (boolean, required): Return only files, exclude directories

• file_extension (string, optional, default=""): Filter files by specified suffix

Success Response:

{
  "res": {
    "success": true,
    "info": {
      "paths": ["/absolute/path/file1.txt", "/absolute/path/file2.js"]
    }
  }
}

fs_copy_directory

Description: Recursively copy full directory tree, support overwriting existing target directories.

Parameters:

• source_dir (string, required): Source directory path

• copy_dest_dir (string, required): Target directory path

• overwrite (boolean, optional, default=false): Clean and overwrite existing target directory

Success Response:

{
  "res": {
    "success": true,
    "info": {}
  }
}

fs_move_directory

Description: Move entire directory tree, fail fast if target path exists to prevent accidental overwriting.

Parameters:

• source_dir (string, required): Source directory path

• dest_dir (string, required): Target directory path

• overwrite (boolean, optional, default=false): Allow overwriting conflicting directory

Success Response: Empty info object with success flag

2. File Basic Operation Tools

fs_create_file

Description: Create empty or content-filled file, auto-create missing parent directories, support multi-encoding.

Parameters:

• file_path (string, required): Target file path

• content (string, optional, default=""): Initial text content

• charset (string, optional, default=utf-8): Encoding enum: utf-8, ucs-2, utf16le, latin1, ascii, base64, hex

Success Response: Empty info object with success flag

fs_delete_file

Description: Delete single regular file only; reject directory paths to avoid batch deletion risks.

Parameters:

• file_path (string, required): Target file path

Success Response: Empty info object with success flag

fs_copy_file

Description: Copy single file with complete metadata retention, support overwrite control.

Parameters:

• source_file_path (string, required): Source file path

• dest_file_path (string, required): Target file path

• overwrite (boolean, optional, default=false): Overwrite existing target file

Success Response: Empty info object with success flag

fs_move_file

Description: Move single file with configurable overwrite behavior.

Parameters:

• source_file_path (string, required): Source file path

• dest_file_path (string, required): Target file path

• overwrite (boolean, optional, default=false): Overwrite conflicting file

Success Response: Empty info object with success flag

fs_get_file_info

Description: Obtain full metadata of file/directory, support optional SHA-256 digest calculation.

Parameters:

• file_path (string, required): Target entry path

• calc_digest (boolean, optional, default=false): Calculate SHA-256 hash

Success Response:

{
  "res": {
    "success": true,
    "info": {
      "absolute_path": "string",
      "is_readable": true,
      "is_writable": true,
      "size": 1672,
      "is_regular_file": true,
      "is_directory": false,
      "is_symbolic_link": false,
      "creation_millis": 1782288135574,
      "last_modified_millis": 1782279393020,
      "last_access_millis": 1782644004556,
      "sha256_digest": "calculated-hash-string"
    }
  }
}

fs_is_file_exists

Description: Lightweight existence check for file or directory.

Parameters:

• file_path (string, required): Target path

Success Response:

{
  "res": {
    "success": true,
    "info": {
      "exists": true
    }
  }
}

3. File Read & Write Tools

fs_read_full_text

Description: Read full text content of target file with specified encoding.

Parameters:

• file_path (string, required): Target file path

• charset (string, optional, default=utf-8): Multi encoding support

Success Response:

{
  "res": {
    "success": true,
    "info": {
      "content": "full-text-file-content"
    }
  }
}

fs_read_text_range

Description: Segmented text reading for large files, support skip leading lines and limit read lines.

Parameters:

• file_path (string, required): Target file path

• lines_to_skip (integer, required): Number of leading lines to skip

• max_lines_to_read (integer, required): Maximum lines to read

• line_separator (string, optional, default="\n"): Line break character

• charset (string, optional, default=utf-8): File encoding

Success Response:

{
  "res": {
    "success": true,
    "info": {
      "lines_count": 5,
      "content": "segmented-text-content"
    }
  }
}

fs_read_binary_chunk

Description: Chunked binary file reading, return Base64 encoded data for safe network transmission, support stream end detection.

Parameters:

• file_path (string, required): Target file path

• bytes_to_skip (integer, required): Leading bytes to skip

• max_bytes_to_read (integer, required): Maximum bytes to read

Success Response:

{
  "res": {
    "success": true,
    "info": {
      "data_base64": "base64-encoded-binary",
      "raw_bytes_length": 5,
      "end_of_stream": true
    }
  }
}

fs_write_text

Description: Write text content to file, support overwrite or append mode.

Parameters:

• file_path (string, required): Target file path

• text (string, required, minLength=1): Text content to write

• append (boolean, optional, default=false): Append mode switch

• charset (string, optional, default=utf-8): File encoding

Success Response: Empty info object with success flag

fs_write_binary

Description: Write Base64 decoded binary data to file, support append operation.

Parameters:

• file_path (string, required): Target file path

• base64_data (string, required, minLength=1): Base64 encoded binary data

• append (boolean, optional, default=false): Append mode switch

Success Response: Empty info object with success flag

4. Search & Replace Tools

fs_search_files_by_content

Description: Recursively scan directory, return all file paths containing target content, support regex, case ignore, suffix filter.

Parameters:

• dir_path (string, required): Scan root directory

• recursive (boolean, required): Recursive scan enable

• search_term (string, required): Search keyword or regex pattern

• is_regex (boolean, optional, default=false): Regex matching enable

• ignore_case (boolean, optional, default=true): Case-insensitive matching

• file_extension (string, optional, default=""): File suffix filter

• charset (string, optional, default=utf-8): File encoding

fs_search_in_files_by_content

Description: Multi-file content matching, return structured results with customizable context lines and result limit.

Parameters:

• dir_path (string, required): Scan root directory

• recursive (boolean, required): Recursive scan enable

• search_term (string, required): Search keyword/regex

• limit (integer, required): Max matching result count

• is_regex (boolean, optional, default=false): Regex enable

• ignore_case (boolean, optional, default=true): Case ignore

• lines_before (integer, optional, default=0): Preceding context lines

• lines_after (integer, optional, default=0): Subsequent context lines

• file_extension (string, optional, default=""): Suffix filter

• charset (string, optional, default=utf-8): File encoding

Success Response:

{
  "res": {
    "success": true,
    "info": {
      "results": [
        {
          "file_path": "/test/file.ts",
          "start_line": 1,
          "end_line": 1,
          "text": "matched-content-line"
        }
      ]
    }
  }
}

fs_search_in_file_by_content

Description: Precise single-file content search with line context preview.

Parameters: Similar to multi-file search, single file path input

Success Response: Structured single-file matching results

fs_file_replace

Description: In-place text replacement in single file, return total replaced count.

Parameters:

• file_path (string, required): Target file path

• search_term (string, required): Text to replace

• replacement (string, required): New replacement text

• line_separator (string, optional, default="\n"): Line break separator

Success Response:

{
  "res": {
    "success": true,
    "info": {
      "count": 1
    }
  }
}

5. Image Processing Tools

fs_image_resize

Description: Resize image with aspect ratio lock support, generate new output image file.

Parameters:

• source_path (string, required): Source image path

• dest_path (string, required): Output image path

• width (integer, required, >0): Target width

• height (integer, required, >0): Target height

• keep_aspect_ratio (boolean, optional, default=true): Lock original aspect ratio

Success Response: Empty info object with success flag

fs_image_crop

Description: Crop specified rectangular region from source image and export new file.

Parameters:

• source_path (string, required): Source image path

• dest_path (string, required): Output image path

• x (integer, required, ≥0): Crop start X coordinate

• y (integer, required, ≥0): Crop start Y coordinate

• width (integer, required, >0): Crop region width

• height (integer, required, >0): Crop region height

Success Response: Empty info object with success flag

fs_image_rotate

Description: Rotate image clockwise by arbitrary degrees, auto expand canvas to preserve full content.

Parameters:

• source_path (string, required): Source image path

• dest_path (string, required): Output image path

• degrees (number, required): Clockwise rotation angle

Success Response: Empty info object with success flag

6. OCR Tool

fs_ocr_extract_text

Description: Extract text from images via Tesseract OCR, support WASM runtime (no local engine) and custom local binary path.

Parameters:

• image_path (string, required): Target image path

• tesseract_bin_path (string, optional, default=""): Custom Tesseract executable path

• tessdata_path (string, optional, default=""): Custom tessdata language resource path

• lang (string, optional, default eng): Recognition language prefix

Success Response:

{
  "res": {
    "success": true,
    "info": {
      "content": "extracted-ocr-text-content"
    }
  }
}

Project Build & Development

Scripts

# Clean build artifacts
npm run clean

# Compile TypeScript source
npm run build

# Watch mode for development
npm run dev

# Full rebuild (clean + build)
npm run rebuild

# Start SSE transport server
npm run server

# FastMCP dev mode
npm run fastmcp

# MCP Inspector debugging
npm run inspect

# Build and run test cases
npm run test

Dependencies

Core Runtime Dependencies

• fastmcp: Official MCP server runtime framework

• sharp: High-performance image processing engine

• tesseract.js: WASM-based cross-platform OCR engine

• winston: Standard logging system

• zod: Strict schema validation for tool parameters

• chardet / iconv-lite: Multi-encoding detection and conversion

• cors: Cross-origin resource sharing support for HTTP transport

• minimist: CLI parameter parsing

License

This project is open-sourced under the Apache License 2.0. See the LICENSE file in the project root for full license details.

Repository & Issues

• GitHub: https://github.com/kurtzhi/fsext-mcp-server-typescript

• Issues: Report bugs or request features