batch_array_add · Frontmatter MCP: Risk & Policy

WHAT IT DOES

What batch_array_add does on Frontmatter MCP

AI agents use batch_array_add 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 batch_array_add needs a policy

The tool adds elements to arrays in frontmatter metadata, which is a reversible modification (Write category). Severity is medium because batch operations could affect multiple documents simultaneously, but changes are not destructive or financial. Confidence is slightly reduced (0.75) due to the empty description, which prevents full confirmation of exact scope and constraints.

From the tool's definition Tool name 'batch_array_add' indicates it modifies array data in batch operations. Server description states it enables 'updating Markdown frontmatter metadata', and this tool is grouped with other batch operations like 'batch_array_replace' and 'batch_update'…

Risk signalsBulk/mass operation — affects multiple targets

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

batch_array_add Rate-limited

batch_array_add 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": {
    "batch_array_add": {
      "limits": [
        {
          "counter": "batch_array_add_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 batch_array_add

What does the batch_array_add tool do? +

batch_array_add. 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 batch_array_add? +

Register the Frontmatter MCP server in PolicyLayer and add a rule for batch_array_add: 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 batch_array_add? +

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

Can I rate-limit batch_array_add? +

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

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

batch_array_add 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.