Which networks does x402 support?
The protocol is network-agnostic. In practice most paid traffic today runs on Base, paid in USDC.
What the protocol allows
x402 identifies networks with CAIP-2 identifiers in the form namespace:reference. Any EVM chain can be expressed as eip155:<chainId>, for example eip155:8453 for Base, and the x402 documentation also defines identifiers for Solana, TON, Algorand, Stellar, Aptos, Hedera, NEAR, Sui, XRPL, Cardano and others. Which of them a given payment can use depends on the facilitator that verifies and settles it.
What Coinbase's facilitator settles
Coinbase's CDP facilitator lists Base (eip155:8453), Base Sepolia (eip155:84532), Polygon (eip155:137), Arbitrum (eip155:42161), Monad (eip155:143), World (eip155:480) and Solana. The exact, upto and batch-settlement schemes run on the EVM networks; Solana supports exact and upto. Coinbase reports more than 100 million facilitator transactions across Base and Solana alone. Other facilitators listed in the x402 documentation support their own sets of networks.
How a buyer learns what an endpoint accepts
Each paid endpoint states its accepted networks in its 402 response: the accepts array has one entry per scheme, network, asset, amount and payTo address. An agent reads that list and pays on a network where it holds funds.
For a new seller, Base with USDC is the common default. It is the network used in Coinbase's and the x402 project's own quickstart and MCP examples, and the one most agent wallets in those examples are funded on.
Take the next step
The pages below go deeper on this question.
Sources and observed evidence
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Publish an x402 API profile with a readiness report and badge
Prepare your x402 API for agent discovery: validate free, inspect readiness evidence, then publish an Ontario service profile for 0.50 USDC only when you need it.
MCP Registry, Smithery or Bazaar: build the agent purchase path
Separate MCP installation from paid API discovery. Give agents a callable tool, free preflight, explicit payment requirements and evidence of fulfilled output.
Can x402 payments be refunded?
An x402 payment is a USDC transfer that is final once it settles, so a refund is a voluntary new transfer and the real protection is a seller that settles after the result exists.
How big is the x402 market?
Coinbase's Bazaar index lists tens of thousands of paid endpoints, but most show one or two payers in 30 days, and repeat demand sits in a few categories.
Are cheaper x402 APIs worse?
Not necessarily; price rarely decides which x402 API agents use, as a reseller that charges more than the original search API and gets more calls shows.
Do Claude or ChatGPT pay for MCP tools?
Claude and ChatGPT can call MCP tools, but neither pays for one by itself; a paid MCP tool needs a client wrapper with a funded wallet and a spending limit.
How do I get my API discovered by AI agents?
Agents search indexes rather than browse websites, so an API is found through Coinbase's Bazaar, x402scan and directories, and through a description that names the task.
How do I know an x402 endpoint is legit?
Three observable checks show whether an unknown x402 endpoint is live, priced as listed and used by repeat buyers; Ontario's finder runs them for 0.005 USDC.