Filter notes by their YAML frontmatter. Supports equality, $in, $exists, $contains predicates. Multiple keys are AND-combined.
AI agents call query_frontmatter to retrieve information from Vault Memory without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and queries metadata from notes without performing any write, destructive, or side-effect operations. It is analogous to a database SELECT query with filtering predicates. The context of a knowledge/notes system and the sibling tools (read_note, list_forward_links, etc.) further confirm this is a read-only retrieval operation. No data is modified, deleted, or executed.
From the tool's definition Tool description states it 'Filter notes by their YAML frontmatter' with various query predicates (equality, $in, $exists, $contains).
Attacks that exploit this kind of access
Filter notes by their YAML frontmatter. Supports equality, $in, $exists, $contains predicates. Multiple keys are AND-combined. It is categorised as a Read tool in the Vault Memory MCP Server, which means it retrieves data without modifying state.
Register the Vault Memory MCP server in PolicyLayer and add a rule for query_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 Vault Memory. Nothing to install.
query_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 query_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 query_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.
query_frontmatter is provided by the Vault Memory MCP server (owrede/vault-memory). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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