// MCP server · card or USDC
Connect eSIM Tabby to Claude and it can search the catalogue, run checkout, and hand back the activation QR code — no tab switching, no copy-pasting order numbers.
Claude Code
Claude web or desktop
Settings → Connectors → Add custom connector. Name it eSIM Tabby and paste the URL below. Claude runs the sign-in flow the first time you use it.
ChatGPT
Settings → Connectors → Create (a Plus/Pro/Business plan with connectors is required). Set the MCP server URL to the address above and choose OAuth for authentication.
Your client runs a secure sign-in flow on first call. We never see your card details. Payment happens on a hosted Stripe page. Using Cursor, ChatGPT or another client? Setup for every agent.
An agent that holds one can settle in USDC over
x402 — HTTP 402, spec v2. Ask for the order with
pay_with="x402" and it comes back with a price and an
x402_url to pay, plus a pay_order tool for clients that
speak x402 natively. Same catalogue, same orders, same QR code at the end.
The buyer signs the transfer, a facilitator broadcasts it, and the USDC goes straight from their wallet to ours. We hold no keys and custody nothing in between. Machine-readable details live in the server card.
I land in Tokyo on Friday for a week. Sort me out with data.
Twelve plans cover Japan. For a week of light use, 3GB at 9.80 USD is the sweet spot — want that one?
Yes, go ahead.
Here's your secure checkout link — I'll pick it up once you've paid.
Paid.
Done — here's your QR code. Scan it to install, or add it manually with the activation code. It'll be live the moment you land.
Same account, same orders. Anything bought in a conversation shows up in the app, and vice versa.
Building an MCP server that takes money
A tool must never charge a card or accept a price as an argument. How one production server authenticates agents, prices orders server-side and survives the retries — with the code.
What happens when an AI agent buys an eSIM with USDC
An agent orders a plan, gets an HTTP 402 quoting USDC on Base, signs the authorisation, and the eSIM is issued. What one production x402 seller sends and receives, and what has broken since going live.
eSIM not working? Find your symptom, then the fix
Nine times out of ten it is data roaming switched off on the travel line. The rest is knowing which of three faults you have — no service, signal but no data, or worked-then-stopped.
How to activate an eSIM on iPhone without a surprise bill
Your travel eSIM needs data roaming on. Your home line needs it off. They are the same-looking toggle one menu apart, and mixing them up is how a $9 trip becomes a $300 one.
eSIM Tabby is run by Josef Rousek, a product engineer based in Prague.