Block until the next SMS arrives (optionally filtered by sim_id) and return its payload. Use this when an agent expects a code/OTP imminently — the call returns synchronously with the message so you don
AI agents call wait_for_next_sms 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.
The tool waits for and retrieves an incoming SMS message, returning its payload. This is a read/fetch operation with no side effects — it does not create, modify, delete, or trigger any external action. The synchronous blocking nature is just a delivery mechanism for reading data. Severity is low since it only reads SMS content, though OTP/code interception could have security implications in adversarial contexts.
From the tool's definition Block until the next SMS arrives (optionally filtered by sim_id) and return its payload
Attacks that exploit this kind of access
Block until the next SMS arrives (optionally filtered by sim_id) and return its payload. Use this when an agent expects a code/OTP imminently — the call returns synchronously with the message so you don. 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 wait_for_next_sms: 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.
wait_for_next_sms 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 wait_for_next_sms 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 wait_for_next_sms. 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.
wait_for_next_sms 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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