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Testing x402 Sandbox Endpoints (Base Testnet)

2026-04-06

The Node4All sandbox is built for real endpoint testing, not placeholder mocks. You can validate the full x402 payment challenge flow against live test networks (starting with Base Sepolia), while still using test funds and a safe integration environment.

Download the Postman collection (WIP)

We published a downloadable Postman collection that includes our currently available sandbox endpoints.

  • Download JSON: node4all-x402.postman_collection.json
  • Import in Postman: In Postman, choose Import → Link, then paste: https://node4all.com/postman/node4all-x402.postman_collection.json

The collection is still WIP and will grow as additional services are released.

Sandbox endpoint overview (quick reference)

  • GET /v1/x402-test  →  301 redirects to GET /v1/coinbase/x402-test
    Primary x402 v2 validation route on Base Sepolia. Facilitated by the Coinbase CDP facilitator. The subdomain implies the network — sandbox = Base Sepolia, api = Base Mainnet. No ?chain=…&network=… query params needed; the server advertises accepted networks in the base64-encoded PAYMENT-REQUIRED response header.

  • POST /v1/md2pdf
    Markdown-to-PDF conversion endpoint available in sandbox mode (free tier limits apply).

  • Sandbox docs: https://sandbox.node4all.com/docs

  • Agent-readable discovery: https://sandbox.node4all.com/.well-known/x402.json and /llms.txt.

Heads up — migration from our earlier receipt flow. Before April 2026 this endpoint used a custom receipt-verification flow (client pays first, submits tx hash in Payment-Signature). It's now x402 v2 spec-compliant (EIP-3009 transferWithAuthorization via the Coinbase CDP facilitator). Solana verification is temporarily removed while we wire it through the v2 accepts[] extension.

MCP + agent toolkit (early access)

We also publish @node4all/x402-agent-toolkit on npmjs. It includes an MCP server so AI agents can call available Node4All sandbox endpoints directly and complete x402 flows with a configured wallet.

This is the fastest path if you want an agent to:

  • discover and call the endpoint tools,
  • handle x402 payment challenges,
  • and execute requests with wallet-backed payment proofs.

A dedicated full post with setup steps, MCP configuration examples, and end-to-end agent flows will follow shortly.

What’s next

A full blog post with complete step-by-step instructions (wallet setup, request/response flow, and troubleshooting) will follow shortly.