AI agents use write-note to create or update resources in Obsidian MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Obsidian MCP Server environment.
This tool creates or modifies notes in an Obsidian vault, which are data modifications. The changes are reversible (notes can be edited or deleted later), placing it in the Write category rather than Destructive. Severity is medium because an AI agent could create or overwrite many notes, potentially cluttering or corrupting a vault, but the damage is not permanent and can be undone.
From the tool's definition Tool description states 'Create or update a note' which directly indicates reversible modification of data. Server description confirms it provides 'write' access to vault files.
Documented attack patterns abuse exactly the kind of access write-note gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Obsidian MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for write-note:
{
"version": "1",
"default": "deny",
"tools": {
"write-note": {
"limits": [
{
"counter": "write-note_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}write-note 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.
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Create or update a note. It is categorised as a Write tool in the Obsidian MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Obsidian MCP Server MCP server in PolicyLayer and add a rule for write-note: 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.
write-note is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the write-note 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.
Set action: deny in the PolicyLayer policy for write-note. 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.
write-note is provided by the Obsidian MCP Server MCP server (piotr1215/mcp-obsidian). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Obsidian MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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9 Obsidian MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.