AI agents use merge_notes 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.
Merging notes creates or modifies data reversibly - the operation combines multiple notes into a single note, which is a write action. While the merge itself isn't directly destructive (notes aren't deleted, just combined), it irreversibly changes the structure and organization of the knowledge base.
From the tool's definition Tool name 'merge_notes' and description 'Merge multiple notes into one' indicates the tool modifies existing notes by combining them. This is a write operation that alters note content and structure.
Documented attack patterns abuse exactly the kind of access merge_notes 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 merge_notes:
{
"version": "1",
"default": "deny",
"tools": {
"merge_notes": {
"limits": [
{
"counter": "merge_notes_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}merge_notes 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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Merge multiple notes into one. 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 merge_notes: 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.
merge_notes 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 merge_notes 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 merge_notes. 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.
merge_notes is provided by the Obsidian MCP Server MCP server (kynlos/obsidian-mcp). 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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120 Obsidian MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.