Callo: pay-per-call for AI agents, settled in USDC on Solana
· Callo
AI agents can read, write, search and trade. The one thing they still can’t do on the internet is pay for it.
The problem
An agent needs a price feed, a search result, a weather lookup. Every API it could use wants an account, an API key, a credit card and a monthly plan. An agent has none of those. So builders either give their API away for free, or lock it behind a signup no bot can finish.
The usual fix is a shared key pasted into a prompt. It’s billed to someone’s card, rate-limited for everyone, and it leaks eventually.
The solution
HTTP 402, finally
HTTP has had a status code for payments since 1997: 402 Payment Required. Nobody used it, because there was no way for a machine to pay a few cents in the middle of a request. Callo uses it through x402.
An agent calls your endpoint. The gate answers 402 with the exact price in USDC. The agent signs a USDC transfer for that amount and sends the same request again with the payment attached. The call goes through. No account, no API key, no invoice.
Paid per call, not per month
Tolls start at a fraction of a cent. Solana settles in well under a second with network fees smaller than the toll, so every single request can pay for itself. An agent pays for exactly what it uses, the moment it uses it.
Checked before it lands
The gate reads every payment before it serves anything. It has to be USDC, sent to that endpoint’s own vault, for at least the quoted amount, and used once for one call. One extra instruction in the transaction and it’s refused. Nothing gets served unpaid.
Launch your endpoint
Point Callo at your API, set your price per call and sign once. Your endpoint gets a gateway URL, its own vault and a pump.fun coin with that vault as creator. Tolls in USDC and the coin’s creator fees land in the same place. You keep 100% of the price you set; Callo’s fee rides on top.
Pair it with a stock
Pick up to three tokenized stocks, like NVDAx, TSLAx or SPYx, and a percentage. That share of everything your vault earns is swapped into those stocks through Jupiter and held. The rest is paid out to you.
Who it’s for
AI agents are about to make more API calls than people do. Callo gives every one of them a way to pay, and every API a way to get paid.
Callo. Every request pays its toll.