A single API purchase is an intent, with policy and limits in front of it. A stream of small calls to one provider is a channel: lock funds once, spend off-chain, settle at the end. A paywall you hit unexpectedly is nanopay, which negotiates and pays without stopping the run. The failure modes are financial, so the structured error codes and the idempotency key matter more here than the tool count.
A payments server for autonomous agents. It fronts a smart contract wallet on Base, with three ways to spend: gateway nanopayments signed offline, policy-checked payment intents, and locked channels for high-frequency micro-transactions.
- nanopay — fetch a 402-protected URL and negotiate the payment inline, topping up from the main wallet when the gateway runs low
- nanopay_activate, nanopay_deposit, nanopay_withdraw and nanopay_balance to manage gateway funds
- submit_intent — a USDC payment run through policy checks and spend limits before it executes
- get_intent and list_intents for the audit trail behind those payments
- open_channel, consume_channel, settle_channel, get_channel and list_channels — lock funds once, pay many times off-chain, settle at the end
- get_balance, get_history and transfer for the ordinary wallet operations
- cross_chain_transfer for a CCTP payment routed to another chain
- smart_fetch, the older HTTP paywall negotiation path
- Structured error codes on failure, so the model can respond to a rejected payment rather than retrying blindly
A Modexia account and an API key. The key's prefix decides the environment — a test key targets the Base Sepolia testnet, a live key targets Base mainnet — so there is no separate switch to get wrong. Runs with uvx. No ETH is needed: gas is sponsored, and every limit is denominated in USDC. Pass an idempotency key on every payment call, because a retried tool call is otherwise a second payment.
One command plus a key — uvx modexia-mcp, then supply credentials