open_file · Obsidian Modified MCP: Risk & Policy

WHAT IT DOES

What open_file does on Obsidian Modified

AI agents invoke open_file to trigger actions in Obsidian Modified. 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 open_file needs a policy

Opening a file triggers an external operation in the Obsidian application (switching the active view/tab to that file), which is more than a passive read — it causes a side effect in the running application. This falls under Execute as it triggers an external UI operation.

From the tool's definition Open a file in Obsidian

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

open_file Rate-limited

open_file 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": {
    "open_file": {
      "limits": [
        {
          "counter": "open_file_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 Obsidian Modified, so you can run agents against it safely.

FAQ

Questions about open_file

What does the open_file tool do? +

Open a file in Obsidian. It is categorised as a Execute tool in the Obsidian Modified MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on open_file? +

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

What risk level is open_file? +

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

Can I rate-limit open_file? +

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

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

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