x402 API pricing: resolve live payment terms before spend.
An x402 API does not have one universal market rate. The safe pattern is to discover the capability for free, inspect its current contract, request the target resource, and authorize only the fresh payment terms returned for that exact call.
Cached “market rate” tables and retired ACP examples are not payment authority. A machine buyer should resolve the exact amount immediately before purchase from the selected target resource.
Base mainnet eip155:8453 · USDC · canonical SqueezeOS payTo 0x5bbd32e0478e49a7540ef2d760e0b0f9aa6328b2.
Discover the capability for free, inspect its public contract and readiness, request the target, parse the fresh PAYMENT-REQUIRED challenge, and authorize only if the caller’s spending policy accepts those exact terms.
Marketing price examples can help compare products, but they must never override fresh runtime terms. An HTTP 402 is a payment requirement, not proof that settlement occurred.
Use the x402 vs API key guide to compare payment models, the x402 USDC API Directory to discover machine-payable capabilities, and AI Agent API Gaps to see where discovery, trust, pricing and proof still break in agent workflows.
Public pricing → · Try before you buy → · x402 Gateway MCP →