Stop the real-time SMS stream and close the WebSocket. Idempotent — safe to call even if no subscription is active.
AI agents call unsubscribe_from_messages to retrieve information from SimRelay MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Even though unsubscribe_from_messages only reads data, uncontrolled read access leaks sensitive information and racks up API costs — an agent caught in a retry loop can make thousands of calls a minute without anyone noticing.
Attacks that exploit this kind of access
Stop the real-time SMS stream and close the WebSocket. Idempotent — safe to call even if no subscription is active. It is categorised as a Read tool in the SimRelay MCP Server MCP Server, which means it retrieves data without modifying state.
Register the SimRelay MCP Server MCP server in PolicyLayer and add a rule for unsubscribe_from_messages: 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 SimRelay MCP Server. Nothing to install.
unsubscribe_from_messages is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the unsubscribe_from_messages 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 unsubscribe_from_messages. 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.
unsubscribe_from_messages is provided by the SimRelay MCP Server MCP server (simrelay/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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