crosspost_message

THE RISK

Medium Risk

Why crosspost_message needs a policy

The tool creates (publishes) message copies in other servers, making it a Write operation rather than Read (it has side effects beyond retrieval). It is not Destructive because the action is reversible (messages can be deleted). It is not Execute because it does not run arbitrary code or commands.

From the tool's definition Publish (crosspost) a message from an announcement channel to all servers following it — the tool modifies the distribution of content by replicating a message to multiple destinations, which is a write operation that creates new instances of the message…

Documented attack patterns abuse exactly the kind of access crosspost_message gives an agent:

POLICY

How to control crosspost_message

PolicyLayer is an MCP gateway — it sits between your AI agents and Discord, and nothing reaches the server without passing your rules. This is the rule we recommend for crosspost_message:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "crosspost_message": {
      "limits": [
        {
          "counter": "crosspost_message_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

crosspost_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.

Create a free account and register Discord — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Discord tools

Destructive bulk_delete_messages Delete multiple messages from a channel at once (2-100 messages). Only works on messages l Destructive delete_automod_rule Delete an auto-moderation rule from the Discord server. Destructive delete_channel Delete a channel from the Discord server. Channel name is fuzzy-matched. Destructive delete_command Delete an application (slash) command. Destructive delete_emoji Remove a custom emoji from the server by name or ID. Destructive delete_event Delete a scheduled event from the Discord server. Destructive delete_forum_tag Remove a tag from a forum channel. Destructive delete_integration Remove an integration from the server by its ID.

All 139 Discord tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about crosspost_message

What does the crosspost_message tool do? +

Publish (crosspost) a message from an announcement channel to all servers following it. It is categorised as a Write tool in the Discord MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on crosspost_message? +

Register the Discord MCP server in PolicyLayer and add a rule for crosspost_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 Discord. Nothing to install.

What risk level is crosspost_message? +

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

Can I rate-limit crosspost_message? +

Yes. Add a rate_limit block to the crosspost_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 crosspost_message completely? +

Set action: deny in the PolicyLayer policy for crosspost_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 crosspost_message? +

crosspost_message is provided by the Discord MCP server (hardheadhackerhead/discord-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Discord tool call.

Start from Discord, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →