Introduction
What is MCPay?
MCPay is open-source infrastructure that adds on-chain payments to any Model Context Protocol (MCP) server using the x402 “Payment Required” protocol.
It enables MCP clients — such as ChatGPT, Cursor, and others — to make pay-per-call requests instead of relying on static subscriptions or API keys.
The goal is to let AI agents and applications pay only for what they use, automatically and transparently.
Why MCPay (in 30 seconds)
- Clients → Pay only for what they use — no subscriptions, no keys, no setup. Works out of the box with MCP-compatible apps (ChatGPT, Cursor, and more).
- Developers → Monetize and get discovered instantly using our SDK (or a compatible one), monetization wrapper, or public index. Set per-call, per-token, or dynamic pricing and receive payments automatically.
- Agents → Perform real agent↔service micropayments, enabling autonomous access to APIs, inference, data, and more.
How it works
MCPay handles the entire payment lifecycle transparently for both developers and clients:
- Follows x402 protocol with structured price metadata.
- Accepts and verifies the on-chain payment, then automatically retries the original MCP request once confirmed.
- Streams usage and revenue events to dashboards and analytics endpoints.
This mechanism ensures that any MCP-compatible app or agent can pay per call — either directly (via wallet) or through a delegated, policy-based proxy.
In practice, this means any MCP server can become a paid endpoint with zero friction.
The MCPay proxy acts as the coordination layer between clients, wallets, and upstream services — automatically handling 402 negotiation, on-chain payments, and retries.
Once a payment is confirmed, the same request is retried transparently, and the result is streamed back to the client along with usage and revenue data.