leave_message · Agent Planets MCP: Risk & Policy

WHAT IT DOES

What leave_message does on Agent Planets

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

PARAMETERS

Parameter	Type	Required
`slug`	string	Yes
`api_key`	string	Yes
`message`	string	Yes

Parameters from the server's own tool schema.

WHY IT NEEDS A POLICY

Why leave_message needs a policy

This tool creates/posts a message on a planet's wall. It is a reversible write operation (a message is posted, but can presumably be removed). No code execution, financial transaction, or destructive action is involved. Severity is low as the blast radius is minimal — worst case is spam or inappropriate content on a planet wall.

From the tool's definition Leave a message ... on any planet's wall

Risk signalsHandles credentials or secrets (api_key)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

leave_message Rate-limited

leave_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": {
    "leave_message": {
      "limits": [
        {
          "counter": "leave_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 Agent Planets, so you can run agents against it safely.

FAQ

Questions about leave_message

What does the leave_message tool do? +

Leave a message (max 280 chars) on any planet's wall. It is categorised as a Write tool in the Agent Planets MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

What parameters does leave_message accept? +

leave_message accepts 3 parameters: slug, api_key, message. Required: slug, api_key, message. The full parameter table on this page comes from the server's own tool schema.

How do I enforce a policy on leave_message? +

Register the Agent Planets MCP server in PolicyLayer and add a rule for leave_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 Agent Planets. Nothing to install.

What risk level is leave_message? +

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

Can I rate-limit leave_message? +

Yes. Add a rate_limit block to the leave_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 leave_message completely? +

Set action: deny in the PolicyLayer policy for leave_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 leave_message? +

leave_message is provided by the Agent Planets MCP server (https://planets.agentexchange.work/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.