Concepts

Concepts: x402, AI Agents, MCP

x402 in one minute

x402 brings “402 Payment Required” to modern APIs. Instead of subscriptions, dashboards, and key rotation, a caller attaches proof of payment to the request. If payment is valid, the request goes through; if not, the server returns 402. In xPay, this is enforced by Faremeter’s middleware on Solana, with USDC as the default token.

Why this matters:

• Per-request pricing that’s simple and transparent

• Works for humans and autonomous agents

• Payments settle instantly to your wallet

AI Agents

Agents are software that browse, plan, and call APIs on their own. They prefer protocols over custom dashboards, and they need pay-per-call rails. x402 is built for this world: agents can find your service, pay for a single call, and move on—no human sign-up or billing.

MCP (Model Context Protocol)

MCP is a standard that lets agents discover and call tools (like your endpoints) in a uniform way. xPay automatically exposes your endpoints as MCP tools, with friendly names, descriptions, and input shapes. Agents can list your tools, select one, pay via x402, and call it - all without bespoke integration work from you.