Pay-per-use SMS sending via x402 crypto payments. Exposes a single send_sms tool that dispatches transactional messages to US phone numbers through a Twilio-backed toll-free gateway. Each send costs $0.03 USDC on Base and automatically appends STOP opt-out language. Currently running on Sepolia testnet while the seller's number clears Twilio TFV approval, so calls return a 503 without charging you until that gate lifts. You supply a funded wallet private key in the MCP config and the server handles payment signing on each invocation. Designed for agent-initiated notifications where you've already collected recipient consent. Rate limits and TCPA compliance checks are baked in. The seller never sees your key; settlement happens on-chain and the receipt comes back with the Twilio SID.
claude mcp add --transport stdio io.github.ultrastarz-x402-sms uvx x402-sms