X402 Sms

Name: X402 Sms
Author: UltraStarz

by UltraStarzversion 0.1.0i★ –iRuns on your computer

Registry nameio.github.UltraStarz/x402-sms

Install

Overview

Description from the maker (original English)

Pay-per-call MCP server. $0.03 USDC sends one transactional SMS to a US phone number via x402.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

User voiceiNo reviews yetReviews open together with accounts in a later step
Our basic checksi1 of 1 passedChecked from public information; code not scanned yet
UsageiVery new↓ 30/wk · ★ –

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Connection: Runs on your computer
Transport: stdio
Category: Chat & email
You need to fill in: BUYER_PRIVATE_KEY

Install

Pick the AI app you use, then copy the settings.

Before you install

Basic checks: 1 of 1 passed
Runs on your computer with your user’s permissions (files, network, apps).
You fill in yourself: BUYER_PRIVATE_KEY

Values marked secret are keys to your account. Never share them or paste them into a chat.

You need

npmNode.js installed (for the npx command)

Which app do you use?

ClaudeClaude CodeCursorVS CodeChatGPT

Pick your app above. We remember it, so next time the button says “Install in …”.

Open Claude Desktop → Settings → Developer → Edit Config, and paste this into claude_desktop_config.json

{
  "mcpServers": {
    "x402-sms": {
      "command": "npx",
      "args": [
        "-y",
        "x402-sms-mcp"
      ],
      "env": {
        "BUYER_PRIVATE_KEY": "your-value"
      }
    }
  }
}

Run this in your terminal

claude mcp add x402-sms --env BUYER_PRIVATE_KEY=your-value -- npx -y x402-sms-mcp

Fill in the empty values before running it.

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "x402-sms": {
      "command": "npx",
      "args": [
        "-y",
        "x402-sms-mcp"
      ],
      "env": {
        "BUYER_PRIVATE_KEY": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "x402-sms": {
      "type": "stdio",
      "command": "npx",
      "args": [
        "-y",
        "x402-sms-mcp"
      ],
      "env": {
        "BUYER_PRIVATE_KEY": "your-value"
      }
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

This one runs on your computer, and ChatGPT can only connect to servers on the internet. Pick another app.

Your choice stays on this device in a cookie; no account needed.

Values you fill in

BUYER_PRIVATE_KEY secret required env
Ethereum private key for the buyer wallet that pays the per-call USDC fee.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Runs on your computer; the tool list appears in your AI app after you install it.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 9, 2026

✓ Pass
Maker matches the repo
The registry name was verified with the GitHub account UltraStarz, which owns the repo
… Not checked yet
Still maintained
We have not read this repo from GitHub yet
… Not checked yet
Has a licence
We have not read this repo from GitHub yet
– Not applicable
Endpoint responds
This one runs on your computer; there is no internet endpoint
– Not applicable
Sign-in with OAuth
Runs on your computer and uses local settings instead
… Not checked yet
No hidden instructions in tool descriptions
Runs on your computer; we can only read tool lists from internet endpoints

Compared with others in Chat & emaili

More stars than 0% of the other 1903 servers in this category
Published to the registry more recently than 8% of the other 1903 servers in this category
Basic checks equal to or better than 100% of the other 1903 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is X402 Sms safe?

It passed 1 of 1 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

You need to fill in: BUYER_PRIVATE_KEY

Does it run on my computer or in the cloud?

It runs on your computer. Your AI app starts it when needed, and data does not pass through the maker’s servers (unless it calls an online service itself).

Is it still maintained?

The GitHub repo last changed –, and the latest version (0.1.0) reached the registry 6 months ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. You also need Node.js on your computer.

What can I use instead?

In the same category: Vexa, emailmd, MCP WhatsApp Cloud

Alternatives

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Reading a card:↓ Downloads per weeki★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

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MCP WhatsApp Cloud

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by codesparEarly↓ 63/wk★ 277Updated 5 months ago

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Install

README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

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 out if 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 /send calls short-circuit to a 503 delivery_pending_tfv_approval response 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):

"mcpServers": { "x402-sms": { "command": "npx", "args": ["-y", "x402-sms-mcp"], "env": { "BUYER_PRIVATE_KEY": "0xYOUR_PRIVATE_KEY" } } } }

Restart your MCP client. A send_sms tool will appear.

What you need

A wallet on Base Sepolia (testnet) funded with:

A small amount of ETH for gas (free from https://www.coinbase.com/faucets/base-ethereum-sepolia-faucet)
USDC for payments (free from https://faucet.circle.com, select Base Sepolia)

Generate a throwaway key:

node -e "const {generatePrivateKey,privateKeyToAccount}=require('viem/accounts');const k=generatePrivateKey();console.log('PRIVATE_KEY=',k);console.log('ADDRESS=',privateKeyToAccount(k).address)"

Use the printed address to claim from faucets, then put the printed key into your MCP config.

Try it

In Claude Desktop, ask:

Text my cell at +15551234567 when this long-running task finishes. The recipient (me) consents to receive this message.

Claude will call send_sms with opt_in_attestation: true. You'll get back a Twilio SID + the on-chain settlement hash. The transfer is visible at https://sepolia.basescan.org.

Compliance — please read

This MCP wraps a regulated SMS gateway. The operator (you) is responsible for ensuring every recipient has consented to receive messages before invoking send_sms. The opt_in_attestation: true argument is your legal attestation under TCPA and CTIA short-code/long-code rules.

Do NOT use this MCP to:

Send marketing or promotional content
Text strangers, scraped lists, or anyone who hasn't opted in
Send to non-US numbers (the seller currently rejects non-+1 E.164)
Send anything related to S.H.A.F.T.-C (Sex, Hate, Alcohol, Firearms, Tobacco, Cannabis)

The seller-side automatically:

Appends Reply STOP to opt out to every message
Honors carrier-level STOP/HELP keyword handling
Logs each send for audit purposes

If you have any doubt about consent, do not call this tool.

Configuration

Env var	Required	Default
`BUYER_PRIVATE_KEY`	yes	—
`SMS_URL`	no	`https://x402-sms-server-production.up.railway.app/send`

To point the MCP server at your own seller deployment, override SMS_URL.

Errors you might see

The MCP surfaces three distinct error shapes so the model can explain what happened to the user and decide whether to retry.

Cause	What you'll see in chat	Was payment taken?
Seller's toll-free number still in TFV review (`HTTP 503`)	"SMS not sent — service is in pre-launch wait" + the seller's submitted date and retry guidance	no
Buyer wallet exceeded per-minute/hour/day rate limit (`HTTP 429`)	"SMS not sent — this buyer wallet hit the per-X rate limit" + `retry_after_seconds`	no
Twilio-side rejection (e.g. invalid number `21211`, opted-out `21610`)	Friendly hint mapped from the Twilio error code + the full response body	yes (the send tried)

For the full mapping of Twilio error codes the MCP recognizes, see TWILIO_HINTS in src/index.ts.

How it works

Claude Desktop ──tool call──> MCP server (this package, on your machine)

│ │ x402 payment (USDC, Base Sepolia) │ + to/message/opt_in_attestation ▼ Public seller (Hono + Twilio on Railway) │ │ Twilio dispatch ▼ SMS lands on recipient's phone │ │ Twilio SID + status ▼ MCP server ──tool result──> Claude Desktop

The MCP server doesn't talk to Twilio directly. It signs an x402 payment with the buyer's wallet, sends the payment + message details to the seller endpoint, and the seller's toll-free number dispatches the SMS. Your private key never leaves your machine. The seller never sees it.

Roadmap

Now (2026-05-22): Base Sepolia testnet, TFV pending. Payment flow verified end-to-end; deliveries gated on Twilio approval.
Once TFV clears: Real US SMS delivery, testnet pricing held while we collect early traffic.
A few weeks out: A2P 10DLC Brand approval → higher per-day throughput tier.
Mainnet flip: Production launch, USDC settles on Base mainnet; Solana facilitator on roadmap after.

License

MIT

X402 Sms

Overview

PopNx MCP’s three pillars

What you can do with it

Install

Before you install

Values you fill in

What it can do

Basic checksi

Maker matches the repo

Still maintained

Has a licence

Endpoint responds

Sign-in with OAuth

No hidden instructions in tool descriptions

Compared with others in Chat & emaili

Common questions

Alternatives

Vexa

emailmd

MCP WhatsApp Cloud

README from the maker

x402-sms-mcp

Install in Claude Desktop / Cursor / Windsurf

What you need

Try it

Compliance — please read

Configuration

Errors you might see

How it works

Roadmap

License