update_frontmatter | PolicyLayer

WHAT IT DOES

What update_frontmatter does on Obsidian Knowledge Management MCP Server

AI agents use update_frontmatter to create or update resources in Obsidian Knowledge Management MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Obsidian Knowledge Management MCP Server environment.

WHY IT NEEDS A POLICY

Why update_frontmatter needs a policy

Updating frontmatter is a reversible write operation that modifies existing data (YAML metadata) without deleting it. Severity is medium because frontmatter corruption could break note relationships (wikilinks, graph operations) or critical metadata, but the effect is limited to a single note and remains recoverable.

From the tool's definition Tool description states 'Update frontmatter fields in a single note' — this directly modifies note metadata. Sibling tool 'bulk_update_frontmatter' confirms this is a modification operation.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_frontmatter Rate-limited

update_frontmatter 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "update_frontmatter": {
      "limits": [
        {
          "counter": "update_frontmatter_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Obsidian Knowledge Management MCP Server, so you can run agents against it safely.

FAQ

Questions about update_frontmatter

What does the update_frontmatter tool do? +

Update frontmatter fields in a single note without touching content. It is categorised as a Write tool in the Obsidian Knowledge Management MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_frontmatter? +

Register the Obsidian Knowledge Management MCP Server MCP server in PolicyLayer and add a rule for update_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 Knowledge Management MCP Server. Nothing to install.

What risk level is update_frontmatter? +

update_frontmatter is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit update_frontmatter? +

Yes. Add a rate_limit block to the update_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.

How do I block update_frontmatter completely? +

Set action: deny in the PolicyLayer policy for update_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.

What MCP server provides update_frontmatter? +

update_frontmatter is provided by the Obsidian Knowledge Management MCP Server MCP server (theoutcastvirus/obsidian-knowledge-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.