rsync · Npm MCP: Risk & Policy

WHAT IT DOES

What rsync does on Npm

AI agents invoke rsync to trigger actions in Npm. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why rsync needs a policy

rsync executes an external shell operation that transfers files between systems. While it has a dry-run safety default, when dryRun=false it performs real file transfers that could overwrite data on remote systems. It spans Write and Execute categories; Execute is most appropriate since it triggers an external operation (rsync process) with effects depending on arguments.

From the tool's definition Syncs files between local and remote locations using rsync... set dryRun=false to actually transfer files

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

rsync Rate-limited

rsync stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "rsync": {
      "limits": [
        {
          "counter": "rsync_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Npm, so you can run agents against it safely.

FAQ

Questions about rsync

What does the rsync tool do? +

Syncs files between local and remote locations using rsync. WARNING: Defaults to dry-run mode for safety — set dryRun=false to actually transfer files. Returns structured transfer statistics. It is categorised as a Execute tool in the Npm MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on rsync? +

Register the Npm MCP server in PolicyLayer and add a rule for rsync: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Npm. Nothing to install.

What risk level is rsync? +

rsync is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit rsync? +

Yes. Add a rate_limit block to the rsync rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block rsync completely? +

Set action: deny in the PolicyLayer policy for rsync. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides rsync? +

rsync is provided by the Npm MCP server (Dave-London/Pare). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.