upsert_note · Obsidian MCP: Risk & Policy

WHAT IT DOES

What upsert_note does on Obsidian

AI agents use upsert_note to create or update resources in Obsidian — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Obsidian environment.

WHY IT NEEDS A POLICY

Why upsert_note needs a policy

This tool performs create-or-update operations (upsert) on notes. While not destructive in the sense of irreversible deletion, it can overwrite existing note content entirely, which is a significant modification with potential data loss if the old content is not recoverable through version control. This is a reversible Write operation since notes can typically be restored from backups or version history in Obsidian.

From the tool's definition The tool description states 'Create a note if missing, replace it if it exists. Body is always fully replaced.' This indicates the tool modifies existing notes by replacing their content entirely.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

upsert_note Rate-limited

upsert_note stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "upsert_note": {
      "limits": [
        {
          "counter": "upsert_note_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about upsert_note

What does the upsert_note tool do? +

Create a note if missing, replace it if it exists. Body is always fully replaced. Frontmatter is replaced by default; pass. It is categorised as a Write tool in the Obsidian MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on upsert_note? +

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

What risk level is upsert_note? +

upsert_note is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit upsert_note? +

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

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

upsert_note is provided by the Obsidian MCP server (yanxue06/obsidian-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.