Save a general knowledge note to Obsidian
AI agents use save_knowledge_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 within an Obsidian vault, which is a reversible write operation. While not destructive (no data loss), it can create unwanted notes that consume storage and potentially pollute the knowledge base. The severity is medium because an agent could spam notes or inject malicious content into the user's vault, but the effects are recoverable by deletion.
From the tool's definition Tool name 'save_knowledge_note' and description 'Save a general knowledge note to Obsidian' indicate creation and persistence of new data in the user's knowledge base.
Documented attack patterns abuse exactly the kind of access save_knowledge_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 save_knowledge_note:
{
"version": "1",
"default": "deny",
"tools": {
"save_knowledge_note": {
"limits": [
{
"counter": "save_knowledge_note_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}save_knowledge_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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Save a general knowledge note to Obsidian. 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 save_knowledge_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.
save_knowledge_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 save_knowledge_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 save_knowledge_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.
save_knowledge_note 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.