FsExt-MCP-Server (Python)

Overview

A full-featured secure MCP server for local file system operations, with built-in image processing, OCR and media tools. Fully compliant with the official Model Context Protocol specification, offering standardized request/response schemas, large-file streaming I/O, multi-transport remote deployment, and comprehensive text search & replace functionality for LLM agent integration.

Core Features

• Full File & Directory Management: Support file creation, deletion, copy, move, metadata query, existence check; full directory tree recursion copy and move with overwrite safety controls.

• Streaming File Read/Write: Integrate full text reading, segmented line-based text reading, chunked binary reading, text/binary overwriting and appending writing, optimized to avoid loading entire large files into memory.

• Powerful Search & Replace: Support directory-wide recursive file content search, single/multi-file contextual matching with configurable pre/post matching lines, regular expression matching, case-insensitive search, and in-place text replacement with match count statistics.

• Image Processing Tools: Built-in high-performance image toolkit powered by Pillow, including resize (aspect ratio lock + canvas padding support), crop, and arbitrary-angle clockwise rotation.

• Native Tesseract OCR Recognition: Reliable text extraction from images dependent on local Tesseract binary installation. No WASM fallback; an empty binary path argument will not trigger alternative JS-based OCR engines. Multi-language tessdata resource support with configurable binary and data paths.

• Strict Input Validation & Unified Response Format: Every tool enables strict additionalProperties: false schema validation to block unexpected input fields. All operations share a universal success/error wrapping structure for consistent client parsing.

• Multi-Transport Support: Compatible with official standard MCP transports: stdio (local desktop client integration), sse (legacy lightweight remote stream), and Streamable HTTP (modern bidirectional remote streaming transport).

• Workspace Security Isolation: Provide --lock-root directory restriction capability. All file/directory operations are strictly confined to the specified root workspace to prevent unauthorized cross-directory path escape attacks.

Related MCP server: MCP Toolkit

Quick Start: Run directly with uvx (No pre-installation required)

uvx automatically pulls the published PyPI package and launches an isolated runtime environment, eliminating manual dependency installation or virtual environment setup.

1. Basic uvx startup commands

Short command (recommended)

# Default stdio mode, unrestricted full filesystem access
uvx fsext-mcp-server

# Lock all operations to a dedicated workspace (production security recommended)
uvx fsext-mcp-server --lock-root /your/workspace

Full complete command

# Stdio mode with workspace isolation
uvx fsext-mcp-server --transport stdio --lock-root /your/workspace

# Remote SSE streaming service
uvx fsext-mcp-server --transport sse --host 0.0.0.0 --port 8000 --lock-root /your/workspace

# Modern Streamable HTTP remote service
uvx fsext-mcp-server --transport http --host 0.0.0.0 --port 8000 --lock-root /your/workspace

2. Integrate FsExt tools with LLM frameworks

No pre-deployment on host machines required; uvx dynamically instantiates the server when an MCP client establishes a connection.

Client config example (Claude Desktop / Cursor MCP json)

{
  "mcpServers": {
    "fsext": {
      "command": "uvx",
      "args": [
        "fsext-mcp-server",
        "--lock-root",
        "/your/workspace"
      ],
      "env": {"PYTHONUTF8": "1"}
    }
  }
}

LangChain / LangGraph core integration snippet

Session lifecycle limitations exist within official langchain-mcp-adapters; complete stable long-connection logic requires extra adapter customization. Below is the standard minimal connection template:

# Core config: Connect to FsExt MCP via uvx stdio transport
server_config = {
    "fsext": {
        "transport": "stdio",
        "command": "uvx",
        "args": ["fsext-mcp-server", "--lock-root", r"/your/workspace"],
        "env": {"PYTHONUTF8": "1"}
    }
}

# Load all exposed filesystem MCP tools
client = MultiServerMCPClient(server_config)
async with client.session("fsext") as session:
    mcp_tools = await load_mcp_tools(session)

# Bind loaded MCP tools to LLM instance for agent workflows
llm = ChatOpenAI(base_url="your-local-llm-api").bind_tools(mcp_tools)

Traditional installation & launch via pip

Install published PyPI package

pip install fsext-mcp-server

Launch commands after pip installation

# Default stdio local mode
fsext-mcp-server-py
fsext-mcp-server

# Short alias
fsext-py
fsext

# Secure workspace locked mode
fsext --lock-root /your/workspace

# Remote SSE streaming server
fsext --transport sse --port 8000

Local source repository development setup

It is recommended to use uv for fast, deterministic environment deployment:

# Clone official source repository
git clone https://github.com/kurtzhi/fsext-mcp-server-python
cd fsext-mcp-server-python

# Install full runtime + dev dependencies
uv sync

Core Runtime Dependencies Description

• chardet: Automatic text file encoding detection

• Pillow: Core image processing backend for resize, crop, rotate pipelines

• python-magic: Accurate cross-platform file MIME type identification

• fastmcp: Official Python MCP server framework

• uvicorn / starlette: HTTP/SSE transport server runtime

• pydantic: Strict schema validation for all tool input parameters

• tesseract: Native bindings for local Tesseract OCR binary

Startup Usage

The server supports three official MCP transport modes and flexible workspace root isolation configuration via CLI flags.

Startup Parameter Reference Table

Common Production Startup Commands

1. Default Local Stdio Mode (for Claude Desktop / Cursor AI Clients)

uv run -m fsext

2. Stdio Mode with Mandatory Workspace Lock (Secure Local Agent Use)

uv run -m fsext --lock-root /your/workspace/path

3. Remote SSE Transport Mode

uv run -m fsext --transport sse --host 0.0.0.0 --port 8000

Access Endpoints

1. SSE long-lived stream subscription channel (server event push): http://<host>:<port>/sse

2. Client JSON-RPC request submission channel: http://<host>:<port>/messages

MCP Inspector Connection Config

• Transport type: SSE

• Connection address input: http://127.0.0.1:8000/sse

4. Standard Streamable HTTP Remote Transport (Modern Bidirectional)

uv run -m fsext --transport http --host 0.0.0.0 --port 8000

Unified Bidirectional Access Endpoint

Single shared entry point for both client requests and server streaming: http://<host>:<port>/mcp

MCP Inspector Connection Config

• Transport type: Streamable HTTP

• Connection address input: http://127.0.0.1:8000/mcp

5. SSE vs Streamable HTTP Transport Feature Comparison

Unified Global Response Specification

All MCP tools share an identical top-level wrapping JSON structure for both successful execution and runtime failure states. Every tool’s business payload is nested within the info sub-object under the root res field.

Core Structure Definition

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

• success: Global operation status flag

  • true: Tool logic executed without exceptions; info contains tool-specific return data

  • false: Operation failed (workspace escape block, missing file, IO error, invalid input schema, permission denied, etc.)

• Dual behavior of info field:

  1. Success mode (success: true): Custom structured business payload unique to each tool

  2. Failure mode (success: false): Fixed standardized error object with machine-readable error code and human-readable explanation

     "info": {
       "code": "ERROR_CODE_IDENTIFIER",
       "message": "Detailed human-readable failure description"
     }

Full Example Responses

1. Successful Response Sample (fs_list_directory)

{
  "res": {
    "success": true,
    "info": {
      "paths": [
        "/tmp/tests/test_util.py",
        "/tmp/tests/__init__.py",
        "/tmp/tests/img/cochem_castle.jpg"
      ]
    }
  }
}

2. Failure Response Sample (Workspace Path Escape Restriction)

{
  "res": {
    "success": false,
    "info": {
      "code": "WORKSPACE_ESCAPE_FORBIDDEN",
      "message": "Access restricted: Path `/tmp/test2` is outside allowed workspace `/tmp/tests`"
    }
  }
}

All tools enforce workspace root isolation and fully follow the standardized input/output schema definitions listed below.

Complete MCP Tools Reference

All tool input schemas enable additionalProperties: false strict validation to reject unrecognized parameters and prevent malicious path injection vectors.

1. Directory Operation Tools

fs_list_directory

Description: Scan target directory recursively or shallowly, return filtered absolute filesystem path list with file-type and extension filtering controls. Parameters:

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

• recursive (boolean, required): Enable full recursive traversal of all subdirectories

• only_files (boolean, required): Filter output to return only regular files, exclude directories

• file_extension (string, optional, default=""): Filter results to files matching the specified suffix extension Success Response Payload:

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

fs_copy_directory

Description: Recursively copy an entire directory tree, with configurable overwrite behavior for pre-existing target directories. Parameters:

• source_dir (string, required): Source directory tree path

• copy_dest_dir (string, required): Target output directory path

• overwrite (boolean, optional, default=false): Clear and overwrite existing destination directory contents Success Response Payload:

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

fs_move_directory

Description: Atomically move an entire directory tree to a new target path. Fails immediately if destination exists unless overwrite is explicitly enabled to avoid accidental data loss. Parameters:

• source_dir (string, required): Source directory path

• dest_dir (string, required): Target directory path

• overwrite (boolean, optional, default=false): Allow overwriting conflicting destination directories Success Response Payload: Empty info object wrapper with success flag.

2. Single File Basic Operation Tools

fs_create_file

Description: Create a new text file, automatically generate missing parent directories, support configurable text encoding and initial file content. Parameters:

• file_path (string, required): Target absolute file path

• content (string, optional, default=""): Initial text content written to the new file

• charset (string, optional, default="utf-8"): Text encoding enum value (full charset list below) Supported Charset Enum Values: utf-8, utf-16, latin-1, iso-8859-1, cp1252, Windows-1252, gbk, gb2312, shift_jis, euc_jp, euc_kr Success Response Payload: Empty info object wrapper with success flag.

fs_delete_file

Description: Permanently delete a single regular file only; rejects directory path inputs to block mass recursive deletion risks. Parameters:

• file_path (string, required): Target regular file absolute path Success Response Payload: Empty info object wrapper with success flag.

fs_copy_file

Description: Copy a single file while retaining original filesystem metadata, with configurable overwrite for conflicting target files. Parameters:

• source_file_path (string, required): Source file absolute path

• dest_file_path (string, required): Target output file absolute path

• overwrite (boolean, optional, default=false): Overwrite pre-existing destination file Success Response Payload: Empty info object wrapper with success flag.

fs_move_file

Description: Atomically move a single file to a new absolute path, with configurable overwrite behavior for conflicting destination files. Parameters:

• source_file_path (string, required): Source file absolute path

• dest_file_path (string, required): Target file absolute path

• overwrite (boolean, optional, default=false): Allow overwriting conflicting destination files Success Response Payload: Empty info object wrapper with success flag.

fs_get_file_info

Description: Retrieve complete metadata for files or directories, with optional SHA-256 cryptographic digest calculation for integrity verification. Parameters:

• file_path (string, required): Target filesystem entry absolute path

• calc_digest (boolean, optional, default=false): Compute SHA-256 hash of file contents Success Response Payload:

{
  "res": {
    "success": true,
    "info": {
      "absolute_path": "C:\\Users\\zhigu\\Documents\\My Games\\fsext-mcp-server\\pyproject.toml",
      "is_readable": true,
      "is_writable": true,
      "size": 1672,
      "is_regular_file": true,
      "is_directory": false,
      "is_symbolic_link": false,
      "creation_millis": 1782288135574.7114,
      "last_modified_millis": 1782279393020.1187,
      "last_access_millis": 1782644004556.3462,
      "sha256_digest": "59614cf5f8ecff38de37637f1d5b6f607d885bd277815786f5ce4bb2ee5b73a6"
    }
  }
}

fs_is_file_exists

Description: Lightweight existence check for any filesystem entry (file or directory) without loading full metadata. Parameters:

• file_path (string, required): Target absolute path to verify Success Response Payload:

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

3. File Read & Write Tools

fs_read_full_text

Description: Read the complete text content of a target file with user-specified text encoding. Parameters:

• file_path (string, required): Target text file absolute path

• charset (string, optional, default="utf-8"): Text encoding enum value Success Response Payload:

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

fs_read_text_range

Description: Stream segmented text reading optimized for large files; skip leading lines and limit total read lines to avoid memory overload. Parameters:

• file_path (string, required): Target text file absolute path

• lines_to_skip (integer, required, minimum=0): Number of initial lines to skip during reading

• max_lines_to_read (integer, required, minimum=0): Maximum total lines to extract from file

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

• charset (string, optional, default="utf-8"): Text encoding enum value Success Response Payload:

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

fs_read_binary_chunk

Description: Chunked streaming read for binary files; returns Base64 encoded byte payloads for safe network JSON-RPC transmission with end-of-stream marker detection. Parameters:

• file_path (string, required): Target binary file absolute path

• bytes_to_skip (integer, required, minimum=0): Number of leading bytes to skip before reading chunk

• max_bytes_to_read (integer, required, minimum=0): Maximum byte length to read in single chunk Success Response Payload:

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

fs_write_text

Description: Write UTF or multi-encoded text content to target file, supporting full overwrite or append-only write modes. Parameters:

• file_path (string, required): Target output file absolute path

• text (string, required, minLength=1): Raw text content to persist

• append (boolean, optional, default=false): Append mode flag (false = overwrite entire file)

• charset (string, optional, default="utf-8"): Text encoding enum value Success Response Payload: Empty info object wrapper with success flag.

fs_write_binary

Description: Decode Base64 encoded binary payload and write raw bytes to target file, supporting append mode for multi-chunk binary uploads. Parameters:

• file_path (string, required): Target output file absolute path

• base64_data (string, required, minLength=1): Base64 encoded raw binary byte payload

• append (boolean, optional, default=false): Append binary data to end of file (false = overwrite) Success Response Payload: Empty info object wrapper with success flag.

4. Content Search & In-Place Replace Tools

fs_search_files_by_content

Description: Recursively scan directory tree and return absolute paths of all files containing matching target text pattern; support regex matching, case insensitivity, and file extension filtering. Parameters:

• dir_path (string, required): Root directory for recursive content scan

• recursive (boolean, required): Enable full subdirectory recursion

• search_term (string, required): Plain text keyword or regular expression pattern

• is_regex (boolean, optional, default=false): Treat search_term as regex pattern when true

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

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

• charset (string, optional, default="utf-8"): Text encoding enum value for file parsing

fs_search_in_files_by_content

Description: Multi-directory bulk content matching, returns structured match results with configurable preceding and trailing context lines around matched content, plus global result count limiting. Parameters:

• dir_path (string, required): Root scan directory absolute path

• recursive (boolean, required): Enable full recursive subdirectory traversal

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

• limit (integer, required): Hard maximum limit on total returned matching entries

• is_regex (boolean, optional, default=false): Enable regular expression matching

• ignore_case (boolean, optional, default=true): Disable case-sensitive matching

• lines_before (integer, optional, default=0): Number of context lines preceding each matched line

• lines_after (integer, optional, default=0): Number of context lines following each matched line

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

• charset (string, optional, default="utf-8"): Text encoding enum value for file parsing Success Response Payload:

{
  "res": {
    "success": true,
    "info": {
      "results": [
        {
          "file_path": "/absolute/path/source.py",
          "start_line": 1,
          "end_line": 1,
          "text": "full-matched-line-content-with-context"
        }
      ]
    }
  }
}

fs_search_in_file_by_content

Description: Precision single-file content search, returns structured matching segments with configurable pre/post context lines for code and document inspection workflows. Parameters:

• file_path (string, required): Target single file absolute path

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

• is_regex (boolean, optional, default=false): Enable regular expression matching logic

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

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

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

• charset (string, optional, default="utf-8"): Text encoding enum value for file parsing Success Response Payload: Structured array of line match objects identical to multi-file search output format.

fs_file_replace

Description: Perform global in-place text replacement within a single target file; return total count of matched and replaced text segments after write. Parameters:

• file_path (string, required): Target editable file absolute path

• search_term (string, required): Text substring to locate and replace

• replacement (string, required): New replacement text payload

• line_separator (string, optional, default="\n"): Line break delimiter for file parsing Success Response Payload:

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

5. Image Processing Tools

fs_image_resize

Description: Resize source image to specified width/height dimensions, with native support for aspect ratio preservation and canvas padding to fill exact target resolution dimensions. Parameters:

• source_path (string, required): Source input image absolute path

• dest_path (string, required): Resized output image absolute path

• width (integer, required, exclusiveMinimum=0): Target pixel width dimension

• height (integer, required, exclusiveMinimum=0): Target pixel height dimension

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

• pad_to_target (boolean, optional, default=true): Add transparent padding to fill exact target width/height when aspect ratio is locked Success Response Payload: Empty info object wrapper with success flag.

fs_image_crop

Description: Extract a rectangular pixel region from source image and export as a standalone output image file. Parameters:

• source_path (string, required): Source input image absolute path

• dest_path (string, required): Cropped output image absolute path

• x (integer, required, minimum=0): Left pixel coordinate of crop region origin

• y (integer, required, minimum=0): Top pixel coordinate of crop region origin

• width (integer, required, exclusiveMinimum=0): Pixel width of cropped rectangular region

• height (integer, required, exclusiveMinimum=0): Pixel height of cropped rectangular region Success Response Payload: Empty info object wrapper with success flag.

fs_image_rotate

Description: Rotate source image clockwise by arbitrary floating-point degree values; automatically expand output canvas dimensions to retain full image content without clipping edges. Parameters:

• source_path (string, required): Source input image absolute path

• dest_path (string, required): Rotated output image absolute path

• degrees (number, required): Clockwise rotation angle in degrees Success Response Payload: Empty info object wrapper with success flag.

6. OCR Text Extraction Tool

fs_ocr_extract_text

Description: Extract human-readable text from raster image files via local Tesseract OCR binary installation. No WASM JavaScript fallback implementation exists; an empty tesseract_bin_path argument will not initialize alternative web-based OCR engines. Parameters:

• image_path (string, required): Input image absolute path for text recognition

• tesseract_bin_path (string, optional, default=""): Absolute path to local Tesseract executable binary; empty value uses system PATH lookup only

• tessdata_path (string, optional, default=""): Absolute directory path containing Tesseract language training data files

• lang (string, optional, default="eng"): Language code prefix matching available tessdata training files Success Response Payload:

{
  "res": {
    "success": true,
    "info": {
      "content": "full-ocr-extracted-text-from-input-image"
    }
  }
}

Project Build & Development Scripts

All standardized npm-equivalent uv development scripts for source repository contributors:

# Clean compiled build artifacts and temporary output directories
uv run -m scripts.clean

# Compile source code and type validation
uv run -m scripts.build

# Watch source files for incremental development rebuilds
uv run -m scripts.dev

# Full rebuild pipeline: clean artifacts + full source compilation
uv run -m scripts.rebuild

# Launch remote SSE transport server instance
uv run -m scripts.server

# FastMCP interactive development mode
uv run -m scripts.fastmcp

# MCP Inspector debug connection launcher
uv run -m scripts.inspect

# Execute full test suite with compiled test artifacts
uv run -m scripts.test

Core Runtime Dependencies

• fastmcp: Official Python MCP server runtime framework

• Pillow: Cross-platform image processing backend for resize, crop, rotate pipelines

• tesseract: Native Python bindings for local Tesseract OCR binary

• chardet: Multi-encoding text file detection

• iconv-lite equivalent backends: Cross-platform text encoding conversion utilities

• cors: CORS middleware for HTTP/SSE remote transport servers

• minimist equivalent CLI parser: Command line argument parsing for startup flags

• pydantic: Strict typed schema validation for all MCP tool input schemas

• uvicorn / starlette: ASGI HTTP server runtime for remote transport deployments

License

This project is open-sourced under the Apache License 2.0. See the LICENSE file located in the project root directory for complete legal license terms and conditions.

Third-Party Component Licenses

This project integrates multiple open-source dependency libraries including chardet, Pillow, python-magic, and Tesseract bindings. All third-party libraries retain their respective original open-source license agreements and copyright statements.

Important Note: No FFmpeg binary artifacts are bundled within this distribution. End users must comply with FFmpeg’s official licensing terms separately if media processing extensions are enabled externally.

Repository & Issue Tracking

• GitHub Source Repository: https://github.com/kurtzhi/fsext-mcp-server-python

• Bug Reports & Feature Requests: https://github.com/kurtzhi/fsext-mcp-server-python/issues