> For the complete documentation index, see [llms.txt](https://docs.rigoblock.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.rigoblock.com/x402-v2-payment-flow.md).

# x402 v2 Payment Flow

1. Make a request → server responds `402 Payment Required` and may include a `PAYMENT-REQUIRED` header describing accepted payment requirements
2. Create the payment payload for USDC on Base (chain 8453), typically with `@x402/core`
3. Retry with the `X-Payment` header → receive structured data; successful 2xx responses may include a `PAYMENT-RESPONSE` settlement receipt

**Use the** [**@x402/core**](https://www.npmjs.com/package/@x402/core) **SDK** — it handles payment flow automatically.

**Payment:** USDC on Base (eip155:8453) — CDP facilitator at api.cdp.coinbase.com

**Integration guide & agent-to-agent architecture:** <https://github.com/RigoBlock/agentic-operator/blob/main/AGENTS.md>

**Supported chains:** Ethereum (1), Base (8453), Arbitrum (42161), Optimism (10), Polygon (137), BNB (56), Unichain (130)