Configurable write permissions for filesystem server

[gar1t]

Is your feature request related to a problem? Please describe.

I'd like to run the filesystem server in a read only mode.

Describe alternatives you've considered

I need to copy any directories that I want to protect from writes to a new directory and mark those files as read only. If anything is written to, it generates an error. As a workaround I put the directory copy under revision control so I can see what was changed and revert it.

[nikaro]

Same, i would like to use the filesystem mcp server in Jan but giving it only read-only access. It would be nice to have a --read-only flag that would disable "write" tools.

[Kobel123]

For anyone landing here now: there are two ways to get a read only setup today without changing the server.

1. Tool annotations. The server marks every tool with readOnlyHint / destructiveHint (see the table in the README). read_text_file, list_directory, search_files etc. are read only; write_file, edit_file, move_file are destructive. Most clients let you turn off individual tools, so switching off the ones that write gets you close to what you asked for.
2. Read only mount. With the Docker setup, add ,ro to the bind mount (type=bind,src=…,dst=/projects/…,ro). Writes then fail at the OS level, whatever the client does.

One caveat from building a permission layer for local files myself: option 1 is a client setting, not a server guarantee. Connect a different client to the same server and all tools are back. If the directory really must not change, option 2 (or OS file permissions) is the boundary you can rely on; the annotations are a convenience on top.