open_file · Obsidian MCP Server MCP: Risk & Policy

WHAT IT DOES

What open_file does on Obsidian MCP Server

AI agents invoke open_file to trigger actions in Obsidian MCP Server. 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

This tool triggers an external operation (opening a file in the Obsidian UI) rather than simply reading or writing data. It causes a side effect in the running Obsidian application via the REST API plugin. It falls under Execute because it performs an action whose effect depends on arguments (which file to open) and manipulates an external application's state.

From the tool's definition "Open a file in Obsidian UI" — triggers an external UI operation in the Obsidian application

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 MCP Server, 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 UI (requires REST API plugin). It is categorised as a Execute tool in the Obsidian MCP Server 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 MCP Server 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 MCP Server. 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 MCP Server MCP server (victors081/obsidian-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.