AI agents use pin_message to create or update resources in Discord — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Discord environment.
Pinning a message modifies channel state and message visibility in a reversible way. It does not delete data (Destructive), execute arbitrary code (Execute), move money (Financial), or merely read (Read).
From the tool's definition Tool description states 'Pin a message in a channel' - this creates/modifies Discord metadata by adding a pinned state to a message, which is a reversible operation (messages can be unpinned).
Documented attack patterns abuse exactly the kind of access pin_message gives an agent:
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 pin_message:
{
"version": "1",
"default": "deny",
"tools": {
"pin_message": {
"limits": [
{
"counter": "pin_message_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}pin_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.
Free to start. No card required.
Pin a message in a channel. 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.
Register the Discord MCP server in PolicyLayer and add a rule for pin_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.
pin_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 pin_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 pin_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.
pin_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.
Start from 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.
139 Discord tools catalogued and risk-classified — across an index of 43,000+ MCP servers.