Purchase a phone number on Twilio
Risk signalsIncurs monthly phone number charges
Part of the Twilio server.
Free to start. No card required.
AI agents use create_incoming_phone_number to initiate financial transactions through Twilio. Financial operations involve real money and are irreversible once processed. PolicyLayer blocks financial tools by default, requiring explicit human approval with transaction-level limits to prevent unauthorised spending.
create_incoming_phone_number moves real money. Without a policy, an autonomous agent could initiate transactions that drain accounts or exceed budgets. PolicyLayer blocks financial tools by default, requiring human-in-the-loop approval with configurable spending limits per transaction and per time window.
Financial tools involve real money. Block by default and require explicit human approval before enabling.
{
"version": "1",
"default": "deny",
"tools": {
"create_incoming_phone_number": {
"deny_if": [
{
"conditions": [],
"on_deny": "Requires human approval."
}
]
}
}
}See the full Twilio policy for all 36 tools.
These attack patterns abuse exactly the kind of access create_incoming_phone_number gives an agent. Each links to the full case and the policy that stops it:
Other financial tools across the catalogue. The same approach applies to each: deny by default, or require human approval.
Purchase a phone number on Twilio. It is categorised as a Financial tool in the Twilio MCP Server, which means it involves financial transactions. Block by default and require explicit approval.
Register the Twilio MCP server in PolicyLayer and add a rule for create_incoming_phone_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 Twilio. Nothing to install.
create_incoming_phone_number is a Financial tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.
Yes. Add a rate_limit block to the create_incoming_phone_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 create_incoming_phone_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.
create_incoming_phone_number is provided by the Twilio MCP server (@twilio-labs/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 36 Twilio tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.