obsidian_register_topic · Obsidian MCP: Risk & Policy

WHAT IT DOES

What obsidian_register_topic does on Obsidian

AI agents use obsidian_register_topic 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_register_topic needs a policy

This tool creates or modifies topic-to-folder mappings in Obsidian's configuration. While it can overwrite existing mappings, the operation is reversible (mappings can be re-registered or deleted). This is a Write operation rather than Destructive since the previous mapping is not permanently lost—it is replaced but the data structure remains intact and can be reconfigured.

From the tool's definition Tool description states it 'registers (or overwrites) a topic → folder mapping', indicating it creates or modifies configuration data. The word 'overwrites' confirms reversible modification capability.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

obsidian_register_topic Rate-limited

obsidian_register_topic 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_register_topic": {
      "limits": [
        {
          "counter": "obsidian_register_topic_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_register_topic

What does the obsidian_register_topic tool do? +

Programmatically registers (or overwrites) a topic → folder mapping in the. 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_register_topic? +

Register the Obsidian MCP server in PolicyLayer and add a rule for obsidian_register_topic: 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_register_topic? +

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

Can I rate-limit obsidian_register_topic? +

Yes. Add a rate_limit block to the obsidian_register_topic 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_register_topic completely? +

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

obsidian_register_topic 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.