AI agents call search_vault to retrieve information from Obsidian MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool searches an Obsidian vault, which is fundamentally a retrieval operation with no side effects. Even though the description is empty, the name and server context (knowledge discovery, filtering, sibling Read tools) strongly indicate this performs search queries across vault content rather than creating, modifying, deleting, or executing operations.
From the tool's definition Tool name 'search_vault' combined with server description indicating 'knowledge discovery and analysis' and 'advanced filtering' suggests querying/searching operations.
Documented attack patterns abuse exactly the kind of access search_vault 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 search_vault:
{
"version": "1",
"default": "deny",
"tools": {
"search_vault": {}
}
}search_vault is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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search_vault. It is categorised as a Read tool in the Obsidian MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Obsidian MCP Server MCP server in PolicyLayer and add a rule for search_vault: 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.
search_vault is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the search_vault 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 search_vault. 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.
search_vault is provided by the Obsidian MCP Server MCP server (pmmvr/obsidian-api-mcp-server). 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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3 Obsidian MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.