Sends a message to a Discord channel using a webhook
AI agents use discord_send_webhook_message to create or update resources in MCP-Discord — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your MCP-Discord environment.
This tool creates new data (a Discord message) in a reversible manner. While sending messages can have social or informational impact, the action itself is not destructive, financial, or code-executing. It fits squarely in the Write category. Severity is medium because an AI agent could spam, impersonate, or flood channels with unwanted messages, but the effects are not permanent and can be deleted by moderators.
From the tool's definition Tool name and description: 'Sends a message to a Discord channel using a webhook' — this is a message creation operation that modifies Discord state by adding content to a channel.
Documented attack patterns abuse exactly the kind of access discord_send_webhook_message gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and MCP-Discord, and nothing reaches the server without passing your rules. This is the rule we recommend for discord_send_webhook_message:
{
"version": "1",
"default": "deny",
"tools": {
"discord_send_webhook_message": {
"limits": [
{
"counter": "discord_send_webhook_message_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}discord_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.
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Sends a message to a Discord channel using a webhook. It is categorised as a Write tool in the MCP-Discord MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the MCP-Discord MCP server in PolicyLayer and add a rule for discord_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 MCP-Discord. Nothing to install.
discord_send_webhook_message is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the discord_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.
Set action: deny in the PolicyLayer policy for discord_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.
discord_send_webhook_message is provided by the MCP-Discord MCP server (barryyip0625/mcp-discord). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from MCP-Discord, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
43 MCP-Discord tools catalogued and risk-classified — across an index of 43,000+ MCP servers.