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x402 Protocol

Status: In development. Nothing on this page is live in production yet. The MCP server and REST API are live and free — x402 is how we plan to charge for premium queries later, without accounts or API keys.

What x402 is​

x402 revives the HTTP 402 Payment Required status code as a machine-payable protocol: a server answers a request with a price and payment instructions, the client pays, retries with proof of payment, and gets the response. It is the emerging open standard for agent payments, governed by the x402 Foundation under the Linux Foundation, with members including Coinbase, Cloudflare, AWS, and Google.

The flow, conceptually:

agent  → GET /api/v1/premium-thing
server → 402 Payment Required  (price, asset, receiver, nonce)
agent  → pays, retries with payment proof header
server → 200 OK  (the data)

No accounts. No bearer keys to leak. Pricing per request instead of per seat — which is the only model that actually fits autonomous agents.

The Cardano story (honest version)​

x402 settlement needs a facilitator — a service that verifies and settles payments so the data server doesn't have to run chain infrastructure. The mainstream facilitator ecosystem (including Coinbase's CDP facilitator) does not support Cardano today.

What does exist on Cardano:

  • Masumi Network's community x402-cardano facilitator — an open-source, community-built facilitator targeting Cardano settlement in USDM and ADA. It is at the testnet proof-of-concept stage.

That's the honest state of the ecosystem: promising, moving, not production. Anyone telling you x402-on-Cardano is production-ready today is selling something.

Basilisk's plan (in development)​

  1. Testnet PoC — put one premium endpoint behind a 402 challenge, settle via the Masumi community facilitator on Cardano testnet (USDM/ADA).
  2. Harden — replay protection, receipt verification, pricing schedule, graceful fallback to the free tier.
  3. Mainnet, carefully — only when the facilitator path is production-grade, and clearly announced when it happens.

Until step 3 ships, every x402 reference in Basilisk is labeled in development — including this page.

What we will not claim​

What we will not claim
  • We will not claim Cardano is officially supported by Coinbase's x402 facilitator or appears on the CDP facilitator list. It is not, and does not.
  • We will not quote x402 transaction-volume statistics as evidence of traction for Cardano agent payments.
  • We will not claim "autonomous mainnet trading" or live autonomous settlement. Today's Basilisk rails are read-only data; settlement work is testnet PoC and research.

If you catch our docs or marketing violating any of these, open an issue — we treat it as a bug.

In the meantime​

You don't need x402 to build on Basilisk today. The MCP server and the free REST API are live, keyless, and cover the same data an x402-gated tier would — just without the premium depth we'll add later.