obsidian_prepend_note · Obsidian MCP: Risk & Policy

WHAT IT DOES

What obsidian_prepend_note does on Obsidian

AI agents use obsidian_prepend_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 obsidian_prepend_note needs a policy

This tool modifies an existing note by inserting content at the top, which is a reversible write operation. It does not delete data, execute code, or involve financial transactions. Misuse could corrupt note content but the operation is reversible by removing the prepended content.

From the tool's definition Inserts content near the top of a note (after frontmatter, if present)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

obsidian_prepend_note Rate-limited

obsidian_prepend_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": {
    "obsidian_prepend_note": {
      "limits": [
        {
          "counter": "obsidian_prepend_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 obsidian_prepend_note

What does the obsidian_prepend_note tool do? +

Inserts content near the top of a note (after frontmatter, if present). 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 obsidian_prepend_note? +

Register the Obsidian MCP server in PolicyLayer and add a rule for obsidian_prepend_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 obsidian_prepend_note? +

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

Can I rate-limit obsidian_prepend_note? +

Yes. Add a rate_limit block to the obsidian_prepend_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 obsidian_prepend_note completely? +

Set action: deny in the PolicyLayer policy for obsidian_prepend_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 obsidian_prepend_note? +

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