Onramp link (fund a wallet with a card)

Generate a single-use Coinbase Onramp URL that lets a human fund any wallet with a card or Apple Pay - the fastest way to put real USDC into an agent's wallet. Send POST /api/onramp-link with the required field address and pay $0.001 per call over x402 or MPP (there is no free tier). It returns a JSON object with onrampUrl, singleUse and note.

Returns the ready-to-open URL, and a fee-inclusive quote when Coinbase provides one. Networks: base, ethereum, polygon, arbitrum, optimism, solana.

Category: Wallet operations · Tags: cdp coinbase wallet onboarding x402 agent-wallet onramp fiat

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Parameters

Example request

curl -i -X POST https://agent402.tools/api/onramp-link \
  -H "Content-Type: application/json" \
  -d '{"address":"0xaBF4FAbd7c416fB67202E5f9002389Fc75e2a9D0","network":"base","amount":"10"}'

Without payment this returns HTTP 402 Payment Required with the exact price for onramp-link; any x402 v2 or MPP client pays it and retries.

Example response

{
  "onrampUrl": "https://pay.coinbase.com/…single-use…",
  "singleUse": true,
  "note": "Open the URL in a browser to complete the purchase - it is single-use and expires after first visit."
}

From an MCP client

catalog.call {
  "slug": "onramp-link",
  "params": {
    "address": "0xaBF4FAbd7c416fB67202E5f9002389Fc75e2a9D0",
    "network": "base",
    "amount": "10"
  }
}

The hosted connector at https://agent402.tools/mcp needs a payment for onramp-link; the stdio package pays it from a wallet or from AGENT402_CREDITS_KEY. Local install: npx -y agent402-mcp.

Errors and behavior

• address is required. An input the tool rejects returns an HTTP 4xx whose body carries error, tool, expected, required and example, so the caller can correct it.
• A paid call that ends in any status of 400 or above is not charged: settlement is cancelled when the tool fails.
• Wallet-only: this tool reaches the network or stored state, so it has no proof-of-work tier. A prepaid card-credits key (Authorization: Bearer a402_...) also pays it.
• A GET or HEAD to /api/onramp-link returns the same 402 quote, so the price can be read without a body.
• An Idempotency-Key header makes a retried paid call replay the first 200 instead of charging again.

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
client.setSpendControls?.(false); // keep your own spending ceiling in code
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/onramp-link", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "address": "0xaBF4FAbd7c416fB67202E5f9002389Fc75e2a9D0",
    "network": "base",
    "amount": "10"
  }),
});

Part of these workflows

Onramp link (fund a wallet with a card) is one step in this skill pack, each sold as a single call:

• Agent wallet readiness check - One call answers 'can this wallet pay right now?' - USDC balances on Base AND Solana, live Base gas, and a ready-to-share Coinbase Onramp funding link if it's running dry.

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