Write · Nexus MCP for Obsidian MCP: Risk & Policy

WHAT IT DOES

What Write does on Nexus MCP for Obsidian

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

WHY IT NEEDS A POLICY

Why Write needs a policy

The Write tool creates new files or overwrites existing ones, which are reversible modifications to data. While overwriting could cause data loss if the user is not careful, the operation itself is not inherently destructive in the sense that it can be undone via version control or undo functions typical in note-taking apps like Obsidian.

From the tool's definition Tool description states 'Create a new file or overwrite existing file'—explicitly performs write operations that modify the vault's file system.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

Write Rate-limited

Write 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": {
    "Write": {
      "limits": [
        {
          "counter": "write_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 Nexus MCP for Obsidian, so you can run agents against it safely.

FAQ

Questions about Write

What does the Write tool do? +

Create a new file or overwrite existing file. It is categorised as a Write tool in the Nexus MCP for 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 Write? +

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

What risk level is Write? +

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

Can I rate-limit Write? +

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

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

Write is provided by the Nexus MCP for Obsidian MCP server (profsynapse/nexus). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.