X402 Agent Skill
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.
Install
one command, takes just this skill from the repositorynpx skills add https://github.com/internet-court/internet-court-skill --skill x402What comes with it
1 065 bytes besides the instructionThe instruction itself
4 sections, as written by the authorx402 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…→ theX-PAYMENTheader.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.
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How to use it
Take internet-court/x402 from the repository into ~/.claude/skills for personal
use, or into .claude/skills inside a project.
The agent identifies a skill by the name field in its header. Two skills with the
same name cannot sit side by side — one of them will be ignored.