reply_to_comment · Figma Comments MCP: Risk & Policy

WHAT IT DOES

What reply_to_comment does on Figma Comments

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

WHY IT NEEDS A POLICY

Why reply_to_comment needs a policy

This tool creates new data (comment replies) in a reversible manner. While it modifies Figma file comments, the action is not destructive—replies can be edited or deleted later. It does not execute arbitrary code, delete data, or move money. The medium severity reflects that misuse could spam or pollute design collaboration channels, but the impact is limited in scope to comment threads and is reversible.

From the tool's definition Tool description explicitly states it will 'Post a reply to an existing comment thread' and 'Requires the Figma token to have the File comments write scope', confirming write capability to Figma files.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

reply_to_comment Rate-limited

reply_to_comment 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": {
    "reply_to_comment": {
      "limits": [
        {
          "counter": "reply_to_comment_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 Figma Comments, so you can run agents against it safely.

FAQ

Questions about reply_to_comment

What does the reply_to_comment tool do? +

Post a reply to an existing comment thread in a Figma file. Use a thread id from the [brackets] in fetch output as comment_id. Requires the Figma token to have the File comments write scope. It is categorised as a Write tool in the Figma Comments MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on reply_to_comment? +

Register the Figma Comments MCP server in PolicyLayer and add a rule for reply_to_comment: 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 Figma Comments. Nothing to install.

What risk level is reply_to_comment? +

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

Can I rate-limit reply_to_comment? +

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

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

reply_to_comment is provided by the Figma Comments MCP server (processedfood/figma-comments-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.