# Antera

> Tool calls for AI agents, paid over x402 in USDC on Base. Every response is checked before the payment settles. If a check fails, the signature is never settled and expires: the agent keeps its money.

## How to call a tool

1. GET the tool's endpoint. A paid tool answers HTTP 402 with one exact price in `accepts`.
2. Sign an EIP-3009 USDC authorization for exactly that amount, to the `payTo` address. Any other amount or payee is refused.
3. Repeat the GET with the payment in the `X-PAYMENT` header (base64 JSON, x402 version 1, scheme "exact").
4. Read the result, the verdict of the 7 checks and the receipt link. Settled only if every check passed.

The same paid request repeated within 10 minutes is answered again at no cost.
No account, no API key, no deposit.

## The 7 checks

delivered in time · price as quoted · no error hidden in a 200 · matches the schema · not empty · no duplicates · data is fresh

## Tools

### Spot price (spot)

The spot price of a crypto asset in US dollars, with the moment it was read.

- endpoint: https://www.antera.sbs/api/call/spot?asset=ETH
- price: $0.0010 per call
- promised failure rate: 1.0 %
- rules: answer within 6 s, data no older than 60 s
- param `asset`: ticker, e.g. ETH, BTC, SOL

### Latest Base block (block)

The newest block on Base: number, hash, time and how many transactions it holds.

- endpoint: https://www.antera.sbs/api/call/block
- price: $0.0010 per call
- promised failure rate: 1.0 %
- rules: answer within 6 s, data no older than 30 s

### Test bench (bench)

A tool that misbehaves on request, so you can watch every check fire for real. Free.

- endpoint: https://www.antera.sbs/api/call/bench?mode=ok
- price: free
- promised failure rate: 0.0 %
- rules: answer within 2.5 s, data no older than 120 s
- param `mode`: ok · schema · empty · error · duplicate · stale · slow · upcharge

## Machine-readable

- https://www.antera.sbs/.well-known/x402 : every resource with its exact x402 payment requirements
- https://www.antera.sbs/api/tools : prices, payees, checks, stakes
- https://www.antera.sbs/api/receipts/{id} : a signed receipt, verifiable with viem verifyMessage
- https://www.antera.sbs/docs : full documentation