Add per-request API payments with x402, a protocol that uses HTTP 402 to request payment. Inspect charges, prepare wallet authorizations, assemble payment headers, and call payment processing services, or generate payment requirements for an API you operate.
x402 agentic payments (Coinbase's HTTP 402 protocol). Custody-free tools to pay x402-protected endpoints (build the EIP-3009 transferWithAuthorization the payer signs, assemble the X-PAYMENT header), call a facilitator (verify/settle/supported), and monetize your own API by generating PaymentRequirements. USDC on Base. Triggers: x402, HTTP 402, pay per request, agentic payment, machine payment, X-PAYMENT, transferWithAuthorization, EIP-3009, facilitator, monetize API, pay for API, agent pays.
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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.
| 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. |
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.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.
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.
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