Pay as an agent

Do you need a Qopper account to pay? No. Any agent from any startup can pay for a product a business sells. There are two paths, and which one you take depends only on one thing: do you want to pay from a Qopper wallet, or from a plain on-chain wallet?

Your agent’s setup	How it pays	Qopper account needed?
Has a Qopper wallet (`qp_sk_`)	`POST .../pay` with a Bearer key, debited from its wallet, checked against its own policy	Already has one
Has any on-chain wallet with USDC (MetaMask, Phantom, a custodial hot wallet…)	x402: sign a USDC transfer and send it in the request	No

The second row is the key one. An agent that is not a Qopper user pays on-chain, and it does not authenticate to Qopper at all — it proves who it is by signing money on the chain. No card, no account creation, no API key.

Prerequisites

You need the checkout URL the business gave you (/checkout/:token), and depending on the path:

Wallet path: a Qopper agent API key (qp_sk_...).
On-chain path: a wallet with USDC on a network Qopper accepts, and the ability to sign a payment payload.

Path A — You have a Qopper wallet

If your agent already runs on Qopper, pay from its wallet. Its own spending policy applies: the payment is checked against per-transaction caps, daily limits and category allowlists, and pauses for human approval if it’s over the threshold.

curl -X POST https://api.qopper.com/checkout/<token>/pay \
  -H "Authorization: Bearer qp_sk_..."

// 200 — paid
{ "paid": true, "charge": { "chargeId": "chg_...", "status": "paid", "method": "ledger" } }

// 402 — over the agent's human-approval threshold
{ "pendingApproval": true, "reason": "Amount exceeds approval threshold", "approvalId": "apr_..." }

The API key IS the identity. Whoever holds it spends from that wallet, so keep it out of logs and rotate it if it leaks.

Path B — You’re not a Qopper user (on-chain)

This is how any agent from any startup pays. It’s HTTP-native: you ask, the server answers with the price, you sign a USDC transfer and retry, and it’s settled. No account, no Qopper citizenship, no API key.

# 1. Ask: you get a 402 with the payment requirements
curl -X GET https://api.qopper.com/checkout/<token>/x402

# 2. Sign a USDC payment and retry with X-PAYMENT to settle
curl -X POST https://api.qopper.com/checkout/<token>/x402 \
  -H "X-PAYMENT: <base64url signed payload>"

The x402 facilitator verifies the signature and funds on-chain, then moves the USDC from your wallet to the business. The only thing you needed was a wallet that can hold and transfer USDC — not a Qopper account.

What does signing actually mean?

Qopper doesn’t host or know your wallet. When you get the 402, it includes the payment requirements — amount, network, destination address. Your agent builds a USDC transfer authorization, signs it with its own wallet key (the same process it would use to move funds anywhere), and sends that signature in the X-PAYMENT header. Qopper checks the signature against the chain, sees the funds are there, and settles. Your wallet was the identity all along.

What you get back

Either path settles the same charge on the merchant side and fires a webhook (charge.succeeded / payment.succeeded). The resource you paid for is yours; the business is notified automatically. The merchant doesn’t care which path you used — the balance is credited the same way.

A single link, many agents

A checkout link is reusable: each paying agent materializes its own charge. If ten agents from ten different startups pay the same link — some with Qopper wallets, some on-chain with no Qopper account — you get ten charges and the merchant sees ten settlements.

Choosing your path

Do you want the payment to go through your Qopper spending policy (caps, categories, human approval)? Use Path A.
Do you have no Qopper account but a wallet with USDC? Use Path B — that’s the “any startup” path.

Checklist before paying

Wallet path: curl -X POST https://api.qopper.com/checkout/<token>/pay with qp_sk_.
On-chain path: GET .../x402 returns a 402? Then sign and retry with X-PAYMENT.
Over your own approval threshold? The payment pauses until a human at your startup approves it — it doesn’t auto-settle.

Checkout reference — the full endpoint details.
x402 payments — how on-chain HTTP payments work.
Accept a payment — the merchant side.

Get Started

Core Concepts

Guides

Pay as an agent

Pay as an agent

Prerequisites

Path A — You have a Qopper wallet

Path B — You’re not a Qopper user (on-chain)

What you get back

A single link, many agents

Choosing your path

Checklist before paying

​Pay as an agent

​Prerequisites

​Path A — You have a Qopper wallet

​Path B — You’re not a Qopper user (on-chain)

​What you get back

​A single link, many agents

​Choosing your path

​Checklist before paying

​Related

Pay as an agent

Prerequisites

Path A — You have a Qopper wallet

Path B — You’re not a Qopper user (on-chain)

What you get back

A single link, many agents

Choosing your path

Checklist before paying

Related