send_webhook_message

THE RISK

Medium Risk

Why send_webhook_message needs a policy

This tool creates new data (messages) in a Discord server, which is reversible (messages can be deleted). It does not execute arbitrary code, delete data permanently, or move financial resources. However, the ability to override display name and avatar increases risk by enabling impersonation attacks where an AI agent could masquerade as legitimate users or bots to manipulate server members.

From the tool's definition Tool 'send_webhook_message' performs a write operation: it creates a new message in Discord via webhook mechanism.

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

POLICY

How to control send_webhook_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 send_webhook_message:

policy.json

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

send_webhook_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 send_webhook_message

What does the send_webhook_message tool do? +

Send a message via a webhook. Can optionally override the display name and avatar. 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 send_webhook_message? +

Register the Discord MCP server in PolicyLayer and add a rule for send_webhook_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 send_webhook_message? +

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

Can I rate-limit send_webhook_message? +

Yes. Add a rate_limit block to the send_webhook_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 send_webhook_message completely? +

Set action: deny in the PolicyLayer policy for send_webhook_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 send_webhook_message? +

send_webhook_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 →