Send a message to another Claude Code instance by peer ID. The message will be pushed into their session immediately via channel notification.
AI agents use send_message to create or update resources in Claude Peers — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Claude Peers environment.
The tool creates new data (a message) in another Claude Code instance's session. While messages are typically reversible and don't cause destructive side effects, sending unsolicited or malicious messages to other agents could cause workflow disruption, prompt injection attacks via message content, or coordination of harmful multi-agent behaviors.
From the tool's definition Tool description states it 'send a message' and 'pushed into their session immediately via channel notification', which creates a new message artifact in another agent's session state.
Documented attack patterns abuse exactly the kind of access send_message gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Claude Peers, and nothing reaches the server without passing your rules. This is the rule we recommend for send_message:
{
"version": "1",
"default": "deny",
"tools": {
"send_message": {
"limits": [
{
"counter": "send_message_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}send_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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Send a message to another Claude Code instance by peer ID. The message will be pushed into their session immediately via channel notification. It is categorised as a Write tool in the Claude Peers MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Claude Peers MCP server in PolicyLayer and add a rule for send_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 Claude Peers. Nothing to install.
send_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 send_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 send_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.
send_message is provided by the Claude Peers MCP server (louislva/claude-peers-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Claude Peers, 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.
4 Claude Peers tools catalogued and risk-classified — across an index of 43,000+ MCP servers.