Networks and Assets

Identifiers

v1 examples often used friendly network names such as base-sepolia. v2 moves to CAIP-2 identifiers so clients, servers, and facilitators can talk about networks without local aliases. EVM chains use eip155:<chainId>. Base mainnet is eip155:8453 and Base Sepolia is eip155:84532.

That matters for agents. A human may understand "Base" from UI context, but software needs a stable identifier to compare against policy. CAIP-2 also makes multi-chain offer lists cleaner because every accepted network can be evaluated uniformly.

Default assets and dollar pricing

The docs support dollar-string pricing such as "$0.01" on networks with preconfigured default assets. Under the hood, that requires token address, decimals, transfer method, and sometimes EIP-712 name/version metadata. For unsupported assets or custom ERC-20 tokens, the seller must supply explicit token information.

USDC appears across many examples because it is stable, widely supported, and has 6 decimal places on the listed default assets. But the protocol direction is asset-agnostic. The right asset is the one your buyer wallets, facilitator, accounting process, and target network can support safely.

• Base mainnet: eip155:8453 with USDC as a listed default asset.
• Base Sepolia: eip155:84532 for testnet development.
• Solana mainnet and devnet use Solana CAIP-2 identifiers tied to genesis hashes.
• Custom ERC-20 pricing needs token address, decimals, and EIP-712 metadata where applicable.

Network tradeoffs

Low fees are not the only selection criterion. For an agent that may make many paid calls, finality, wallet tooling, facilitator support, token liquidity, availability of testnet funds, compliance needs, and transaction observability all matter. A network that is cheap but poorly supported by your buyer wallet may be worse than a slightly more expensive path with reliable tooling.

Solana ecosystem materials emphasize low cost and fast finality for high-frequency agent payments. EVM ecosystems emphasize broad wallet and middleware support. Stripe, Coinbase, Cloudflare, and chain-specific docs show that x402 is becoming a cross-provider pattern rather than a single-chain project.