https://api.circuit.org, with users approving at https://app.circuit.org. Paper money keeps every trade and agent simulated while you build.
Use paper money
When you connect, turn off every wallet. The permit then covers only paper money, so every trade and agent runs on simulated funds. Ask for paper explicitly, for example “Start Macro Trend with $1,000 of paper money”. Paper agents showwalletId: null.
A permit with wallets trades with real money. Pick no wallets until you mean to trade.
Watch a working integration
Pinewood is a demo app built on this API. It shows every call it makes, with its request, response and timing. Open it next to your own app to compare. Each response carriesx-circuit-request-id; include it when you report a problem.