sync · Joplin MCP: Risk & Policy

WHAT IT DOES

What sync does on Joplin

AI agents invoke sync to trigger actions in Joplin. 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 sync needs a policy

The sync tool executes an operation that interacts with external systems (the configured sync target). While it doesn't directly modify local data (that's handled by write tools like create_note, edit_note), it triggers and executes a synchronization process whose side effects depend on the state of both local and remote data.

From the tool's definition Tool description: 'Trigger a Joplin sync to push/pull changes with the configured sync target' - uses 'trigger' and performs push/pull operations to external systems

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

sync Rate-limited

sync 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": {
    "sync": {
      "limits": [
        {
          "counter": "sync_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 Joplin, so you can run agents against it safely.

FAQ

Questions about sync

What does the sync tool do? +

Trigger a Joplin sync to push/pull changes with the configured sync target. It is categorised as a Execute tool in the Joplin MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on sync? +

Register the Joplin MCP server in PolicyLayer and add a rule for sync: 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 Joplin. Nothing to install.

What risk level is sync? +

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

Can I rate-limit sync? +

Yes. Add a rate_limit block to the sync 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 sync completely? +

Set action: deny in the PolicyLayer policy for sync. 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 sync? +

sync is provided by the Joplin MCP server (joplin-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.