Transactional SMS delivery for developers, part of the tollkit.dev family of paid developer tools. Messages are delivered via a Twilio toll-free verified sender to US recipients who have explicitly opted in.
x402-sms is a pay-per-call SMS API. Developers integrate it into AI agents and applications via an open-source MCP client; their wallet pays a small USDC fee per send. The service is operated as a sole proprietorship under the tollkit.dev brand by UltraStarz.
Sender number: +1 (888) 841-3236 (Twilio toll-free, TFV-verified)
Service URL: sms.tollkit.dev
Operating brand: tollkit.dev
Contact: hello@tollkit.dev
If you have opted in to receive messages from x402-sms, you will receive transactional SMS notifications from +1 (888) 841-3236 — order updates, system alerts, security notifications, account messages, two-factor codes, and similar event-triggered content. Message frequency typically ranges from 1 to 10 messages per month.
Representative messages sent through the service:
Your order #4521 has shipped. Track: https://example.com/t/4521. Reply STOP to opt out.Your verification code is 729104. Reply STOP to opt out.Alert: payment for invoice #883 failed. Please retry. Reply STOP to opt out.x402-sms does not send marketing or promotional content. Content related to S.H.A.F.T.-C (sex, hate, alcohol, firearms, tobacco, cannabis) is prohibited at the API and rejected at the gateway.
To receive messages from x402-sms, complete the consent form at /optin. The form discloses business identity, message type and frequency, message and data rates, STOP/HELP keywords, and links to the privacy policy and terms of service. An unchecked consent checkbox is required to submit.
At any time, reply STOP to a message from +1 (888) 841-3236 to unsubscribe. Twilio honors carrier-level opt-out keywords (STOP, UNSUBSCRIBE, CANCEL, END, QUIT). To request removal outside of the STOP keyword, email hello@tollkit.dev.
Reply HELP to any message from +1 (888) 841-3236 for assistance, or email hello@tollkit.dev. Message and data rates may apply.
Opt-in form · Privacy Policy · Terms of Service
x402-sms is consumed via the open-source x402-sms-mcp package, which mounts as a tool in Claude Desktop, Cursor, or Windsurf. The protocol is HTTP 402 with EIP-3009 USDC payment authorizations; the seller calls Twilio after compliance and payment checks. Full product details and the umbrella brand at tollkit.dev.