Agent Wallet

An agent wallet is a crypto wallet whose signing key is available to an AI agent's runtime, so the agent can pay for things without a human approving each transaction. In the x402 ecosystem it typically holds USDC on Base, because that pairing makes payments as small as $0.01 economically viable — fees on Base are a fraction of a cent and settlement takes about two seconds.

The wallet is identified by its address, which is what a paid API or MCP server sees as the payer. The agent itself has no bank account and no credit card; the wallet is its entire financial identity.

Traditional payment methods assume a human in the loop: a checkout page, a card form, a 3-D Secure prompt. An autonomous agent calling fifty paid endpoints in a minute cannot stop for any of that. A wallet lets it respond to an HTTP 402 challenge by signing a payment authorization programmatically and retrying the request — the entire exchange happens between machines.

Per-call payment also sidesteps the alternative: provisioning an API key and a subscription for every service the agent might conceivably touch. With a funded wallet, the agent discovers a tool, pays for exactly the calls it makes, and moves on.

The typical flow has three steps. First, the operator provisions a wallet — either a raw keypair managed by the agent framework or a managed wallet service that keeps keys in custody. Second, they fund it with USDC on Base; a few dollars covers hundreds of calls at typical per-call prices. Third, they grant the agent's runtime access to sign x402 payment authorizations, usually behind spending controls.

Spending limits are the critical safety layer: per-call caps, daily budgets, and allowlists of payee addresses keep a misbehaving or compromised agent from draining the balance. The wallet signs only what policy permits.

When an agent calls a paid MCP server or API listed on the Loomal Index, the server replies with a 402 response carrying the price and payment address. The agent's wallet signs that payment requirement, the request retries with the payment header attached, and USDC settles on Base before the handler runs. The agent receives the tool result plus an Ed25519 signed receipt and a transaction hash — a verifiable audit trail of what its wallet spent and why.

Because settlement is final, there are no chargebacks; the wallet's on-chain history is the ledger of record for everything the agent bought.

Treat the agent wallet like a metered expense account, not a treasury: keep only working capital in it, top it up automatically, and rotate keys if the runtime environment may have been exposed. Reconcile spend against the signed receipts your agent collects — each one ties a payment to a specific call, which is what makes per-call budgeting auditable in a way subscription bills never were.