Paying with x402

The consumer of this API is not a company, it is a loop. An agent evaluating whether to place a $2M order should be able to spend a fraction of a cent finding out what that order fills at — and that transaction cannot require a signup flow, a key rotation policy, a procurement conversation, or a human.

The flow#

1. 1

   Call the endpoint

   No credentials. A priced endpoint answers 402 Payment Required with the amount, currency and network in the response headers.

2. 2

   Pay

   The agent settles the stated amount in USDC on the stated network.

3. 3

   Retry with the receipt

   Repeat the request with the payment proof attached. The endpoint returns 200 and the data.

GET /v1/exit/aave-v3-weth?size_usd=5000000 HTTP/1.1
Host: api.crifine.app

HTTP/1.1 402 Payment Required
X-Payment-Amount: 0.004
X-Payment-Currency: USDC
X-Payment-Network: base
X-Payment-Recipient: 0x…

# agent settles, then retries with proof

GET /v1/exit/aave-v3-weth?size_usd=5000000 HTTP/1.1
Host: api.crifine.app
X-Payment-Proof: 0x…

HTTP/1.1 200 OK
Content-Type: application/json

What each tier costs#