Get all unique values for a specific frontmatter key
AI agents call get_metadata_values to retrieve information from Obsidian Local REST API MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries and retrieves frontmatter metadata values from notes without creating, modifying, deleting, or executing any operations. It is a read-only information retrieval operation with no side effects. The low severity reflects minimal blast radius—an AI agent cannot cause data loss, code execution, or unintended modifications through this tool.
From the tool's definition Tool name 'get_metadata_values' and description 'Get all unique values for a specific frontmatter key' indicate retrieval of existing metadata without modification or deletion.
Documented attack patterns abuse exactly the kind of access get_metadata_values gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Obsidian Local REST API MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for get_metadata_values:
{
"version": "1",
"default": "deny",
"tools": {
"get_metadata_values": {}
}
} get_metadata_values is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get all unique values for a specific frontmatter key. It is categorised as a Read tool in the Obsidian Local REST API MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Obsidian Local REST API MCP Server MCP server in PolicyLayer and add a rule for get_metadata_values: 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 Local REST API MCP Server. Nothing to install.
get_metadata_values 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 get_metadata_values 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 get_metadata_values. 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.
get_metadata_values is provided by the Obsidian Local REST API MCP Server MCP server (j-shelfwood/obsidian-local-rest-api-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Obsidian Local REST API 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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13 Obsidian Local REST API MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.