ObserverSAFE
An MCP server that provides server-to-client notifications for file changes that the client subscribes to
Overview
From the repository's own README, as read at the audited commit. Badges and raw HTML are left out.
mcp-observer-server is an MCP (Model Context Protocol) server that monitors file system events and provides real-time notifications to MCP clients. It acts as a (more bi-directional) bridge between your local file system and AI assistants like ~~Claude~~ Inspector, enabling them to respond to file changes automatically.
NOTE: This is a demo/POC of a file monitoring MCP server that I'm working on. I'm seeing a lot of questions/comments/Issues/Discussions about this kind of thing, so I wanted to post this minimal implementation to share my approach.
Context
The MCP protocol defines the notion of a resource subscription, wherein a client can request to be notified of any changes to a resource, and the server can choose to send notifications. Here is the flow diagram:
The protocol says the client should then send a read request back to the server to read the changes. (All of this is optional, by the way). But, I find this a bit cumbersome, and involves an extra trip, and I'd rather have my resource-update notification describe the change as well. Fortunately, the SDK offers a meta/_meta field and you can pretty much send whatever you want. So I might want to send the number of lines changed, a diff of the changes, who knows what. I haven't implemented that in this demo, right now I'm just sending the timestamp. (I basically ripped everything out from the server except the minimum POC.) Also, it's just running on stdio transport, nothing fancy.
NOTE!!! I haven't tested this with any "real" MCP clients yet - my understanding is that very view clients actually support resource subscriptions, since it's optional anyway. However, fortunately
7a80a33b6c6fOBSERVED · 2026-10-10Connect
Built from this server's own package name, version and transport as found in its source — not copied from anyone's documentation, so it cannot drift against a page we do not control.
claude mcp add mcp-observer-server -- uvx mcp-observer-server
{
"mcpServers": {
"mcp-observer-server": {
"command": "uvx",
"args": [
"mcp-observer-server"
]
}
}
}Exposed tools (4)
4 read · 0 write · 0 destructive.
| Tool | Risk | Description |
|---|---|---|
list_watched | read | List all currently monitored paths and their subscriber counts |
subscribe | read | Subscribe to changes on a file or directory |
subscribe_default | read | Subscribe to the default watched.txt file for development |
unsubscribe | read | Unsubscribe from changes on a file or directory |
Trust audit
SAFEgrade B · trust 89/100 Nothing in the source contradicts what it says it does. Grade A is reserved for packages that have also passed the behavioural sandbox.
| Layer | What it checks | Result |
|---|---|---|
| L0 | Provenance & inventory | PASS |
| L1 | Static analysis of the code | PASS |
| L2 | Instruction surface (what it tells the agent) | PASS |
| L3 | Class-specific surface | PASS |
| L4 | Behavioural (sandbox) | SKIPPED |
What the source does
- Filesystem
- none-observed
- Network
- none-observed
- Shell
- none-observed
- Dependencies
- pinned
- Secrets in source
- none-found
Findings (1)
.pre-commit-config.yaml
Gates applied: no_behavioural_pass.
7a80a33b6c6ffull audit observations/trust-audit/mcp-server/hesreallyhim__observer.json · Report an issue / request a re-scanAudit history
Every audit this server has had. A grade with a past is a grade somebody is still checking.
| Date | Source | Verdict | Grade | Score | Change |
|---|---|---|---|---|---|
| 2026-10-10 | 7a80a33b6c6f | SAFE | B | 89 | first audit |
Questions
What is the Observer MCP server?
An MCP server that provides server-to-client notifications for file changes that the client subscribes to
What tools does Observer expose?
4 in total: 4 read-only, 0 that write, and 0 that can delete or overwrite. Every one is listed on this page with its risk.
Is Observer safe to connect to an agent?
The audit found nothing in the source that contradicts what it says it does, and graded it B (89/100). Grade A is held back for packages that have also passed a sandboxed behavioural run, which is why a clean server reads B.
What credentials does Observer need?
No credential environment variables were found in its source, so it appears to need none.
How does Observer run?
It speaks stdio, so it runs as a local process your client starts. It is published on PyPI as mcp-observer-server.
How current is this page?
The grade is for one exact copy of the source (7a80a33b6c6f), read on 2026-10-10. The repository is watched and re-audited when it changes.