MCP Desktop Extension

Filesystem + Exec

Filesystem tools and optional command execution for Claude Desktop, jailed to directories you choose.

What this extension does

Filesystem + Exec is a local MCP server packaged as a .mcpb Desktop Extension. Once installed, it gives Claude two sets of capabilities:

Filesystem tools (always on): read, write, edit, search, move files, and walk directory trees — restricted to one or more directories you approve during setup.
Command execution tools (off by default): run_bash, run_shell, run_cmd, run_powershell, and run_command, which run real shell commands on your machine.

Command execution is high-privilege. When enabled, the connected AI agent can run any command your user account can run — installing packages, deleting files, changing settings — with no sandboxing beyond the working-directory restriction on the exec tools' cwd. Leave this off unless you have a specific reason to enable it, and only use it with clients you trust.

Installing

Download the latest .mcpb file from the GitHub Releases page.
In Claude Desktop, go to Settings → Extensions → Advanced settings → Install Extension…
Select the downloaded .mcpb file.

You'll be prompted to configure:

Setting	Description
Allowed Directories	One or more folders the server may access. Nothing outside these is reachable.
Enable command execution	Off by default. Turn on only if you need the exec tools above.

Restart Claude Desktop if prompted, then look for the tools icon in the chat input to confirm it's connected.

Available tools

Always available:

Tool	Purpose
`read_text_file`	Read a text file, optionally just head/tail N lines
`read_media_file`	Read an image/binary file as base64
`read_multiple_files`	Read several files in one call
`write_file`	Create or fully overwrite a file
`edit_file`	Targeted find/replace edits, with dry-run preview
`create_directory`	`mkdir -p` semantics
`list_directory`	Shallow directory listing
`list_directory_with_sizes`	Shallow listing with file sizes, sortable
`directory_tree`	Recursive JSON tree of a directory
`move_file`	Move or rename a file or directory
`search_files`	Recursive case-insensitive filename search
`get_file_info`	Stat a path — size, timestamps, permissions
`list_allowed_directories`	Show the configured allowed root directories

Only present when command execution is enabled:

Tool	Purpose
`run_bash`	Run a command via `/bin/bash -c` (macOS/Linux)
`run_shell`	Run a command via `/bin/sh -c` (POSIX)
`run_cmd`	Run a command via Windows `cmd.exe` (Windows only)
`run_powershell`	Run a command via PowerShell (`powershell.exe` on Windows, `pwsh` elsewhere)
`run_command`	Generic — pick the shell explicitly: bash, sh, cmd, or powershell

Platform notes

Filesystem tools work identically on Windows, macOS, and Linux. For the exec tools:

run_cmd only works on Windows — on macOS/Linux it returns a clear error instead of failing silently.
run_powershell requires PowerShell Core (pwsh) to be separately installed on macOS/Linux; it is not bundled.
run_bash and run_shell work natively on macOS and Linux, and require WSL or Git Bash on Windows.

Example prompts

List everything in my allowed project folder.
Read the first 20 lines of config.yaml.
Find every file with "test" in the name under this directory.
Rename draft.md to final.md.

Troubleshooting

If tools don't appear after install, fully quit and reopen Claude Desktop (not just close the window).
A PathAccessError means a requested path fell outside your configured allowed directories — add the directory via the extension's settings rather than trying alternate paths.
Enable debug logging in Claude Desktop's settings to see extension-level logs if a tool call fails unexpectedly.