update · Frontmatter MCP: Risk & Policy

WHAT IT DOES

What update does on Frontmatter MCP

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

WHY IT NEEDS A POLICY

Why update needs a policy

The tool performs reversible modification of Markdown frontmatter metadata. While the description is empty, context from the server description and sibling tools (batch_update, batch_array_* operations) clearly indicates write capability.

From the tool's definition Tool name is 'update' on a server that 'Enables querying and updating Markdown frontmatter metadata'; sibling tools include batch_update, batch_array_add, batch_array_remove, batch_array_replace indicating write operations against document metadata

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update Rate-limited

update 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": {
      "limits": [
        {
          "counter": "update_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 Frontmatter MCP, so you can run agents against it safely.

FAQ

Questions about update

What does the update tool do? +

update. It is categorised as a Write tool in the Frontmatter MCP 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? +

Register the Frontmatter MCP server in PolicyLayer and add a rule for update: 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 Frontmatter MCP. Nothing to install.

What risk level is update? +

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

Can I rate-limit update? +

Yes. Add a rate_limit block to the update 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 completely? +

Set action: deny in the PolicyLayer policy for update. 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? +

update is provided by the Frontmatter MCP server (kzmshx/frontmatter-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.