Swap a phone number on an existing order. Gets a new number for the same service and country without additional charge. Use when the current number isn't receiving SMS. Cooldown: swap is only available 120 seconds after purchase. Check swap_available_at on the order before calling. Calling earlie...
Part of the Sms server.
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AI agents call virtualsms_swap_number to retrieve information from Sms without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though virtualsms_swap_number only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"virtualsms_swap_number": {}
}
}See the full Sms policy for all 18 tools.
These attack patterns abuse exactly the kind of access virtualsms_swap_number gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Swap a phone number on an existing order. Gets a new number for the same service and country without additional charge. Use when the current number isn't receiving SMS. Cooldown: swap is only available 120 seconds after purchase. Check swap_available_at on the order before calling. Calling earlier returns a cooldown_active error from this MCP server (no backend round-trip).. It is categorised as a Read tool in the Sms MCP Server, which means it retrieves data without modifying state.
Register the Sms MCP server in PolicyLayer and add a rule for virtualsms_swap_number: 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 Sms. Nothing to install.
virtualsms_swap_number 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 virtualsms_swap_number 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 virtualsms_swap_number. 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.
virtualsms_swap_number is provided by the Sms MCP server (virtualsms-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 18 Sms tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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