| name | x402 |
| description | x402 agentic payments using Coinbase's HTTP 402 protocol. Provides custody-free tools to pay x402-protected endpoints by building the EIP-3009 transferWithAuthorization payload, signing it, and assembling the X-PAYMENT header; call facilitator verify, settle, and supported operations; and monetize APIs by generating PaymentRequirements. Supports USDC on Base. Use for x402, HTTP 402, pay-per-request, agentic or machine payments, X-PAYMENT, transferWithAuthorization, EIP-3009, facilitators, API monetization, and agents paying for APIs. |
x402 Payments skill
x402 turns HTTP 402 Payment Required into a real payment rail for agents: a
server replies 402 with what it wants paid; the client signs an off-chain
authorization and retries with an X-PAYMENT header; a facilitator broadcasts
it. Settlement uses EIP-3009 transferWithAuthorization (e.g. USDC on Base) —
the facilitator can only broadcast the signed authorization, never alter the
amount or destination.
Custody-free: the plugin builds the EIP-712 the payer signs and assembles
the header; it never holds a key.
Tools
| Tool | Purpose |
|---|
chaingpt_x402_decode | Decode a 402 body or X-PAYMENT header into human terms (amount/token/recipient/expiry) before paying. |
chaingpt_x402_build_payment | Build the UNSIGNED EIP-3009 typed data; pass a signature back to get the final X-PAYMENT header. |
chaingpt_x402_facilitator | Call a facilitator: supported / verify / settle. |
chaingpt_x402_create_requirements | Server side: generate the PaymentRequirements + 402 body to monetize your endpoint. |
chaingpt_x402_fetch | The whole client loop in one tool: fetch a URL; on 402 it decodes the challenge and (given from) emits the unsigned typed data; re-call with xPaymentHeader to complete the paid request. |
Pay an endpoint (client flow)
Fast path — one tool drives the loop:
chaingpt_x402_fetch url=<resource> from=<payer> → on 402 you get the decoded price/payee AND the unsigned EIP-3009 typed data.- Sign the typed data in the payer's wallet.
chaingpt_x402_build_payment from=<payer> requirements=<from step 1> signature=0x… → the X-PAYMENT header.chaingpt_x402_fetch url=<resource> xPaymentHeader=<header> → the paid response.
Manual path (same primitives, finer control): _decode → _build_payment → sign → _build_payment +signature → retry yourself.
Monetize your endpoint (server flow)
chaingpt_x402_create_requirements network=base amount=0.01 payTo=<you> → serve
the returned JSON with HTTP 402. Verify/settle incoming payments via a
facilitator (chaingpt_x402_facilitator).
Known EIP-3009 tokens: USDC on base and base-sepolia. For other tokens pass
full PaymentRequirements (with asset + extra.name/extra.version).
0 ChainGPT credits.
