AI agents call search_in_frontmatter 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 through YAML frontmatter metadata in Obsidian notes. Search operations are read-only queries with no side effects—they retrieve and filter existing data without creating, modifying, or deleting content. The low severity reflects minimal risk even if an AI agent misuses it; the worst outcome would be returning unintended metadata to the user.
From the tool's definition Tool name 'search_in_frontmatter' and description 'Search YAML frontmatter specifically' indicate a query/search operation that retrieves data without modification.
Documented attack patterns abuse exactly the kind of access search_in_frontmatter 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_in_frontmatter:
{
"version": "1",
"default": "deny",
"tools": {
"search_in_frontmatter": {}
}
}search_in_frontmatter is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Search YAML frontmatter specifically. 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_in_frontmatter: 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_in_frontmatter 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_in_frontmatter 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_in_frontmatter. 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_in_frontmatter 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.