update_message · Follow Plan MCP Server MCP: Risk & Policy

WHAT IT DOES

What update_message does on Follow Plan MCP Server

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

WHY IT NEEDS A POLICY

Why update_message needs a policy

This tool creates or modifies data reversibly by updating message content. It does not delete data (which would be Destructive) nor does it execute arbitrary code or trigger external operations (which would be Execute). The blast radius is medium because message modifications could affect communication history and project documentation, but changes are reversible via further updates or backups.

From the tool's definition Tool name is 'update_message' and description states 'Update an existing message'. This modifies existing data (the message content) in a reversible manner.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_message Rate-limited

update_message 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_message": {
      "limits": [
        {
          "counter": "update_message_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 Follow Plan MCP Server, so you can run agents against it safely.

FAQ

Questions about update_message

What does the update_message tool do? +

Update an existing message. It is categorised as a Write tool in the Follow Plan 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_message? +

Register the Follow Plan MCP Server MCP server in PolicyLayer and add a rule for update_message: 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 Follow Plan MCP Server. Nothing to install.

What risk level is update_message? +

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

Can I rate-limit update_message? +

Yes. Add a rate_limit block to the update_message 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_message completely? +

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

update_message is provided by the Follow Plan MCP Server MCP server (vibeclasses/follow-plan-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.