X402 Sms
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.
- tool
- 1
- auth
- Secret needed
- transport
- STDIO
- env var
- 1
- last updated
- May 15, 2026
Tools
1 toolsPublic tool metadata for what this MCP can expose to an agent.
send_smsSends a transactional SMS via the seller's toll-free number to a US phone number, costing $0.03 USDC per message paid via x402.
Sends a transactional SMS via the seller's toll-free number to a US phone number, costing $0.03 USDC per message paid via x402.
No parameter schema in public metadata yet.
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BUYER_PRIVATE_KEY*secretEthereum private key for the buyer wallet that pays the per-call USDC fee.
Readme
x402-sms-mcp
A paid MCP server that lets AI agents send SMS messages to US phone numbers.
Each send_sms tool call:
- Sends a transactional SMS via the seller's toll-free number (Twilio verification in progress)
- Auto-appends
Reply STOP to opt outif the body doesn't include opt-out language - Costs $0.03 USDC per message, paid automatically from the configured wallet via x402
No API keys. No Twilio account. The agent pays the toll, the message goes out.
Status (2026-05-22): Public beta on Base Sepolia (testnet). The seller's toll-free number is undergoing Twilio TFV approval (submitted 2026-05-14, still in queue). During this window
/sendcalls short-circuit to a503 delivery_pending_tfv_approvalresponse before the buyer wallet signs anything, so no USDC is moved. The day Twilio approves the number, delivery flips on; pricing flips to Base mainnet shortly after.
Install in Claude Desktop / Cursor / Windsurf
Add this to your MCP config (~/Library/Application Support/Claude/claude_desktop_config.json on macOS):
Details
- Repository
- github.com/ultrastarz/x402-sms-mcp
- Category
- Communication & Messaging
- Package
x402-sms-mcp- Transport
- STDIO
- Auth
- Required
- Registry
- MCP registry, active
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