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x402

Capminal x402 Overview

Pay-as-you-go access to premium API features with onchain payments. x402 makes every request simple, transparent, and wallet‑native.

x402 V2 Upgrade

  • As of December 17, 2025, we have upgraded our x402 APIs to version 2 (V2).

  • Backward compatibility is supported for clients using version 1 (V1), so existing integrations do not require any changes.

  • However, we strongly recommend upgrading to V2 to ensure better compatibility with future x402 API updates.

What is x402?

x402 extends HTTP 402 Payment Required to gate API access with onchain micropayments. Your client first gets a 402 with payment instructions, completes a quick wallet payment, then retries the same request with a cryptographic proof in the X-PAYMENT header.

Pricing

  • Price: Depend on each API

  • Network: Base

  • Pricing can evolve; always trust the live 402 instructions returned by the API

How it works

  1. Call a protected endpoint (e.g., /x402/research) without X-PAYMENT.

  2. Receive 402 Payment Required with live payment instructions (price, network, recipient, time window, etc.).

  3. Pay using a compatible wallet/client.

  4. Retry the exact same request with X-PAYMENT: <payment-proof>.

  5. We verify onchain proof, s and return 200 OK with the result.

Header

  • X-PAYMENT: Cryptographic proof of payment sent on retry.

Under the hood

  • Standardized 402 responses include machine‑readable payment requirements

  • Secure, server‑side verification of the X-PAYMENT proof.

  • Settlement on Base mainnet in USDC for low fees and speed

We are using Coinbase CDP's x402 facilitator to verify partner transactions, read detail HERE

Where it’s used

x402 API host endpoint: https://www.capminal.ai/api/x402/

  1. GET ${host}/research — Token research with AI deep search analysis (x402‑protected).

  2. T.B.U (we will release soon)

  3. T.B.U (we will release soon)

Quick start for partners

  • Build a two‑step client: handle 402 → pay → retry with X-PAYMENT

  • Show a wallet deep link or QR to streamline checkout

  • Keep the original request inputs identical on retry

Following Coinbase Docs:

LogoQuickstart for Buyers - Coinbase Developer DocumentationCoinbase Developer Documentation

Status codes at a glance

  • 200 OK: Payment verified and request processed

  • 402 Payment Required: Missing/invalid payment or not yet paid

  • 400 Bad Request: Invalid inputs

  • 500 Internal Server Error: Something went wrong server‑side

Security & reliability

  • Proofs are verified server‑side against onchain intent

  • No long‑lived secrets required for protected endpoints

  • Payments settle on a reliable L2 (Base) with predictable fees

Integration tips

  • Handle the 402 → pay → retry loop seamlessly in your UI

  • Cache user inputs between the two calls

  • Show clear progress states during payment and verification

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