Everything you need to use it, and to build on it.

Hood USDB is a privacy-first payments platform on Robinhood Chain, an Ethereum Layer-2 built on Arbitrum technology. You deposit, hold, send, request and withdraw without publishing your financial activity to a block explorer.

• Two assets. USDG — the Global Dollar stablecoin — for dollar-denominated payments, and native ETH for anything routed through the privacy pool.
• A privacy level per action. Public, Partial or Full. You pick per payment, and the level determines the asset, the settlement path and what an observer can see.
• Custody. You connect your own wallet and sign every deposit and withdrawal; we never hold your keys. Your balance itself sits in a pooled reserve Hood USDB operates and is recorded on our ledger, so withdrawals are processed by our backend rather than claimed from a contract. That is a trust assumption, and you should weigh it.
• No accounts, no KYC. Your wallet is your identity. An optional @username makes you payable by name.
• Programmable. Agents can hold scoped API keys with hard spending policies and transact on your behalf.

1. 01Connect a walletOpen the dashboard and click Connect. If your wallet does not have Robinhood Chain yet, the app offers to add it.
2. 02Sign inYou sign a plain text message containing a one-time nonce. This is a signature, not a transaction — it costs nothing and moves nothing. It proves you control the wallet and opens a session.
3. 03Claim a usernameIn Settings, pick an @username of 3–20 characters. Other users can then pay you by name instead of a 0x address, and your address stays off their screen.
4. 04Fund the walletYou need ETH on Robinhood Chain for deposits and gas. Bridge in via the canonical Arbitrum bridge or a third-party bridge that supports the chain.

Every movement of money happens at one of three levels. The level determines the asset, the settlement path, and what an outside observer can see.

How full privacy works

A full-privacy deposit is sent to a fresh, one-time holding address generated for that deposit alone. From there the funds are forwarded through a mixing stage in randomized portions and land in a pooled reserve with no on-chain edge back to your depositing wallet. Your spendable balance is then tracked on the private ledger — so when you pay another user, nothing touches the chain and there is nothing for a block explorer to pair.

The dashboard shows two balances: USDG from public and partial deposits, and ETH from full-privacy deposits. The ETH balance is ledger-based — the sum of your deposits, incoming and outgoing transfers and withdrawals, maintained off the public chain.

• Transfers between Hood USDB users settle instantly on the ledger — no gas, no fee, no on-chain trace.
• Withdrawals pay out real on-chain ETH from the pooled reserve, which has no link to your original deposit.
• The eye toggle hides every amount on screen, rendered as ••••, which is what you want when you are screen-sharing.

Full privacy — ETH

1. 01Choose Full in the deposit modalThe asset switches to native ETH.
2. 02Enter an amountMinimum 0.003 ETH. The app checks your wallet holds the amount plus a gas headroom before asking you to sign.
3. 03Sign one plain ETH transferIt goes to your one-time holding address.
4. 04The pipeline takes overForwarding, mixing and crediting happen automatically. The modal tracks progress; your balance credits when mixing completes, typically a few minutes.

Public and Partial — USDG

USDG deposits route through the deposit contract: approve, then deposit. Partial deposits enter the shared pool; public deposits stay fully visible. Both credit your USDG balance.

Send from the Payments tab or the Send modal. There are two recipient modes.

• @username. A live lookup confirms the user exists, and warns you if they have not deposited yet, since a recipient needs a balance history to receive ledger credits. The recipient's wallet address is never revealed to you — resolution happens server-side.
• 0x address. Validated as an EVM address. If it belongs to a Hood USDB user they are credited in-app; if not, you are pointed to Withdraw instead, because external payouts are withdrawals.

The asset follows your privacy level: Full sends ETH from your private balance — instant, feeless, no on-chain footprint. Partial and Public send USDG. Every send requires a wallet signature authorising the exact amount and recipient.

Payment requests follow the x402 pattern: a payee creates a priced request, shares it, and anyone can settle it. Use them for invoices, for services, or for machine-to-machine pay-per-call.

A pay link sends money to someone who does not use Hood USDB yet. You attach an amount to a one-time link and share it over any channel.

• Claiming in-app. The recipient connects a wallet and the amount credits to their balance instantly.
• Claiming on-chain. The recipient pastes an address and receives an on-chain payout instead.
• Safety net. Unclaimed links refund to the sender automatically after seven days.

While a link is outstanding the amount is held in escrow on the ledger, so you cannot double-spend it.

Move funds from your private balance back on-chain, from the Withdraw tab or the balance card.

ETH withdrawals

• Paid as native ETH from the pooled reserve — the paying wallet has no on-chain connection to your deposit.
• Fee 1.5%, shown before you confirm. Any positive amount up to your balance.
• Withdrawing to a fresh wallet gives you a clean break: the receiving address has no history linking it to you.

USDG withdrawals

USDG pays out on-chain through the pool contract, with the fee displayed at confirmation.

The Terminal is a conversational interface to your wallet. It answers read-only questions directly — balances, recent activity, token details — and for anything transactional it opens a pre-filled form that you confirm and sign yourself.

• “What is my balance?” reads your USDG and ETH balances.
• “Send 0.001 to @alice” opens the Send form pre-filled. You always sign.
• “Show my last 5 transactions” summarises your history.
• “Create a payment request for 10” opens the request form.

The Agents tab lets you create agents that transact on your behalf, with limits you control. An agent never holds your keys; it holds a scoped API key whose every action is checked against your spending policy server-side and logged.

All agent endpoints authenticate with the agent's API key via the X-Agent-Key header, or Authorization: AgentKey <key>. The key identifies the agent, so no IDs appear in URLs. All amounts are ETH.

curl https://hoodusdp.com/api/agents/budget \
  -H "X-Agent-Key: <key>"

{
  "success": true,
  "policy": { "max_per_tx": 0.1, "daily_limit": 0.5, "allowed_tokens": ["ETH"] },
  "spent_today": 0.0003,
  "daily_remaining": 0.4997,
  "eth_balance": 0.0030,
  "spendable_now": 0.0030
}

curl -X POST https://hoodusdp.com/api/agents/transfer \
  -H "X-Agent-Key: <key>" \
  -H "Content-Type: application/json" \
  -d '{ "to": "@alice", "amount": 0.001, "token": "ETH" }'

{ "success": true, "signature": "<settlement ref>", "amount": 0.001 }

curl -X POST https://hoodusdp.com/api/agents/pay-request \
  -H "X-Agent-Key: <key>" \
  -H "Content-Type: application/json" \
  -d '{ "request_id": "x402_abc123" }'

{
  "success": true, "status": "settled",
  "amount": 0.0001, "token": "ETH",
  "receipt": "<base64url payload>.<signature>",
  "receipt_signer": "0x..."
}

curl -X POST https://hoodusdp.com/api/agents/withdraw \
  -H "X-Agent-Key: <key>" \
  -H "Content-Type: application/json" \
  -d '{ "to": "0x...", "amount": 0.001, "token": "ETH" }'

Errors

Every agent request-payment returns a cryptographically signed receipt — proof of settlement a payee can verify before delivering a service. A receipt is base64url(payload) + "." + signature, signed by the platform receipt signer under EIP-191.

curl -X POST https://hoodusdp.com/api/x402/verify-receipt \
  -H "Content-Type: application/json" \
  -d '{ "receipt": "<receipt>" }'

{ "valid": true, "settlement": "settled", "signer": "0x...",
  "payment": { "payment_id": "...", "amount": 0.0001, "token": "ETH" } }

import { verifyMessage } from "ethers"

const [payload, signature] = splitAtLastDot(receipt)
const signer = verifyMessage(payload, signature)
// valid if signer === the receipt_signer returned at payment time

const details = JSON.parse(atob(payload)) // amount, token, payment_id