replace · Obsidian Local MCP: Risk & Policy

WHAT IT DOES

What replace does on Obsidian Local

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

WHY IT NEEDS A POLICY

Why replace needs a policy

This tool modifies note content reversibly through search-and-replace operations. While it changes existing data, it does not permanently delete or destroy information (Destructive), nor does it execute arbitrary code (Execute). It fits Write category as it updates/modifies content.

From the tool's definition Tool description explicitly states it performs 'find and replace text inside an Obsidian note' and uses 'app.vault.read/modify'. The 'modify' operation and the nature of replacing content confirms data modification capability.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

replace Rate-limited

replace 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": {
    "replace": {
      "limits": [
        {
          "counter": "replace_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 Local, so you can run agents against it safely.

FAQ

Questions about replace

What does the replace tool do? +

Find and replace text inside an Obsidian note using eval with app.vault.read/modify. It is categorised as a Write tool in the Obsidian Local MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on replace? +

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

What risk level is replace? +

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

Can I rate-limit replace? +

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

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

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