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U.CASH Developers · SDK & integrations

Build on open money infrastructure.

Zero-dependency SDKs, an MCP server, OpenAPI, and the HTTP-402 / UCP rails. Multi-coin, non-custodial. Funds always settle to your own wallet.

Read the docs → npm i agents-u-cash
~/sdks · agents-u-cash
$ npm i agents-u-cash added 1 package in 1.4s $ pip install agents-u-cash Successfully installed agents-u-cash > const { UcashSDK } = require('agents-u-cash') > await new UcashSDK({ apiKey: 'uxc_...' }).createResource({ amount: 5, asset: 'usdc_base' })
JS + Python MCP server (79 tools) OpenAPI 3.1 HTTP-402 + UCP 13 e-commerce plugins Non-custodial
What it is

One interaction layer, every surface

Ship payments across registries with one interaction layer. The agents-u-cash JavaScript and Python SDKs (zero-dependency, on npm and PyPI), a 79-tool MCP server, and an OpenAPI 3.1 spec cover the full sell and buy surface. Underneath sit the HTTP-402 and UCP merchant rails: multi-coin detect, card redirect, and gasless USDC-on-Base exact settlement, all non-custodial. For storefronts, 13 e-commerce plugins plug the same engine into existing carts.

How it works

Install, create, verify, settle

Install the SDK

Add the client from npm or PyPI, or copy the single dependency-free file. Authenticate with an API key (sell) or no key (buy). The JS and Python APIs mirror each other in camelCase and snake_case.

Create a checkout

Set your receive address, then create a priced resource or one-off payment request. You get a pay.u.cash checkout_url or /id/ link, the 402 door a buyer opens.

Customer pays

A human opens the HTML checkout; an agent fetches the ?agent=1 JSON manifest; an x402 client sends an X-PAYMENT header. The buyer pays direct to your address, on-chain, in any supported coin.

Verify the webhook

pay.u.cash detects the on-chain transfer and posts an HMAC-signed settlement webhook to your URL. Verify the signature with your webhook secret; the buyer can also submit the tx hash to settle instantly.

Settle to your wallet

Funds move direct buyer to seller. The platform holds no balance and signs no value move. The fee is debited from prepaid seller credit, never split on-chain. Read your settlement log via the SDK or MCP.

One surface, four ways in

The same calls everywhere

Whether you use the JS SDK, the Python SDK, the MCP server, or the REST API, the merchant surface is the same.

Capability
JS SDK
Python SDK
MCP server
REST API
Priced 402 resources
createResource
create_resource
uxc_create_resource
POST /v1/resources
View door + settle
viewDoor + verify
view_door + verify
uxc_view_door
GET /r/{id} + /v1/verify
Payment request
createPaymentRequest
create_payment_request
uxc_create_payment_request
POST /v1/payment-requests
UCP checkout
create / complete / get
create / complete / get
uxc_create_checkout
POST /checkout-sessions
Scoped subagent keys
createSubagent
create_subagent
uxc_create_subagent
POST /v1/subagents
x402 gasless settle
verify (auto)
verify (auto)
uxc_verify_payment
POST /v1/exact-settle
Capabilities

What the SDK can do

Zero-dependency clients

The JS SDK (Node 18+ and browsers, global fetch) and Python SDK (3.7+) ship as single files with no dependencies. Install from npm or PyPI, or copy the file in. MIT licensed.

HTTP-402 priced resources

Create a resource, get a 402 door with a multi-coin accepts[] list. A buyer pays the exact amount to a unique address; the platform detects the on-chain transfer and settles.

UCP checkout sessions

Run multi-item, mixed-currency carts over the Universal Commerce Protocol. Create, complete, then poll the order for per-item fulfillment.

x402 gasless USDC on Base

The exact rail: a buyer signs an off-chain EIP-3009 transferWithAuthorization, a seller-funded relayer submits it on Base. The buyer pays no gas and sets no approval.

79-tool MCP server

A stdio MCP server (JSON-RPC 2.0) exposes the seller and buyer surface to Claude Desktop and any MCP client. Configure wallets, create resources, run UCP checkouts.

Scoped subagent keys

Delegate a limited sa_ API key with a built-in staff role (clerk, teller) or a custom permission set. RBAC enforces the capability set on every endpoint; store_scope restricts it.

Full merchant surface

Beyond 402 resources, manage the whole account: transaction history and CSV export, refunds, webhook resend, multi-store CRUD, shop products, landers, and billing.

OpenAPI 3.1 spec

A 34-path OpenAPI 3.1 spec, served live at agents.u.cash/openapi.json, covers Account, Storefront, Sell (402), Buy, UCP, and Subagents. Generate a client in any language.

E-commerce plugins

Drop U.CASH into your cart

13 open-source plugins plug the same non-custodial engine into existing platforms. Each uses your store's Cloud token to create checkouts and your webhook secret to verify settlement. Funds settle direct to your wallet.

WooCommerce Shopify Magento 2 PrestaShop OpenCart CS-Cart Shopware 6 VirtueMart Drupal Commerce Zen Cart WHMCS Blesta Invoice Ninja

Plus 125+ integrations across billing, memberships, frameworks, AI agents, and mobile.

Browse all integrations
How it fits in U.CASH

The SDK and the rest of the network

The SDK is the developer door over the agents and pay rails.

U.CASHcore
WooCommerce
Shopify
Magento 2
WHMCS
npm + PyPI
MCP server
+120 more
FAQ

Questions, answered

Is U.CASH custodial?
No. The platform never holds funds or private keys. Crypto settles direct from buyer to the address you control; cards run through your own Stripe account. The x402 default verify path confirms the on-chain transfer and never signs a value move.
Which coins are supported?
About 40 native coins: Bitcoin plus Lightning, Ethereum and 15 EVM L2s, Solana, Tron, XRP, Monero, USDT, USDC (including gasless USDC on Base), and UCASH. You can also accept self-serve custom tokens (ERC-20, TRC-20, SPL) on 20 chains.
Do the e-commerce plugins need an API key?
No. Each plugin uses your store's publishable Cloud token to create checkouts, and your Webhook secret to verify settlement. The Shopify order pay-link app additionally uses pay.u.cash's server-side capture against your Shopify orders.
How do scoped subagent keys work?
An owner mints a limited sa_ key with a built-in role or custom permission set. It authenticates against your tenant, but RBAC enforces the capability set on every endpoint and store_scope can restrict it to specific stores. Owner-only to create.
Can I use the MCP server with non-Claude clients?
Yes. The server speaks MCP over stdio with newline-delimited JSON-RPC 2.0, so any MCP client works. Point it at the PHP server with your UXC_API_KEY; seller tools need the key, buyer and UCP tools are public.

Build on open money

Zero-dependency SDKs, an MCP server, OpenAPI, and the HTTP-402 rails. Non-custodial, multi-coin.

Read the docs → About U.CASH Agents