MCPay

MCPay is open-source payment infrastructure that enables AI agents and MCP (Model Context Protocol) clients to pay for individual API calls on-chain using stablecoins, replacing subscriptions and API keys with a pay-as-you-go micropayment model.

The Problem: AI Agents Can't Pay for What They Use

Modern AI agents and applications routinely need to call external APIs to retrieve real-time data, run specialized tools, or access third-party services. The prevailing model for this access — monthly subscriptions or static API keys — creates friction on both sides. Providers overbundle access into flat-rate plans, while AI clients end up paying for capacity they never consume. There is no standard mechanism for an AI agent to autonomously pay a few cents for a single API call, verify the payment, and retry the request without human involvement.

MCPay addresses this gap. It implements the x402 protocol, a micropayment standard built on top of HTTP's long-dormant 402 "Payment Required" status code, to enable per-call monetization of any MCP server or API endpoint. The result is a coordination layer that allows AI clients — including integrations with ChatGPT and Cursor — to pay only for what they use, automatically and verifiably.

How x402 Works

The x402 protocol, specified by Coinbase in May 2025, repurposes HTTP 402 to carry on-chain payment metadata. MCPay implements this protocol across a five-step payment flow:

1. A client calls a protected route on an MCPay-monetized server.
2. The server returns HTTP 402 with a payment-required envelope: price, accepted tokens, and recipient wallet.
3. MCPay's proxy or SDK negotiates the payment terms and signs an on-chain stablecoin transfer authorization.
4. The on-chain payment settles; the client includes proof-of-payment in a retry request.
5. The server verifies the proof and returns the full response.

This flow is transparent and requires no manual intervention. Payments route directly to the provider's wallet with no intermediary cut taken by MCPay.

Components

MCPay ships as a monorepo with four main components:

Registry. A publicly accessible, machine-readable index of MCPay-monetized MCP servers at v2.mcpay.tech/servers. It is searchable by humans and queryable by AI agents discovering which tools are available and at what price.

Monetizer (Proxy). A no-code proxy layer that wraps existing API endpoints or MCP servers and enforces per-call pricing without requiring changes to the upstream service. Providers set flat fees, per-token costs, or dynamic pricing; MCPay handles the rest.

TypeScript SDK. A programmatic integration library that allows developers to define paid tools directly in code, specifying pricing per tool or per call. The SDK handles the full x402 lifecycle, including payment negotiation, on-chain verification, and automatic retry logic.

CLI. A local proxy tool for adding x402 payment enforcement to remote MCP servers. The CLI is aimed at developers who want to quickly test monetized endpoints without deploying infrastructure.

Supported Networks and Tokens

MCPay operates across both EVM-compatible chains and Solana. EVM support covers Base, Avalanche, IoTeX, and Sei. Solana support includes both mainnet and devnet, making it usable in production and testing environments. Accepted payment tokens are USDC and EUROe — both stablecoins, which avoids the price volatility that would make per-call micropayments impractical.

The multi-chain design reflects a deliberate choice: providers and clients should not be forced onto a single network. An agent running on a Solana-native application can pay for a tool call without bridging to an EVM chain.

For Providers and Consumers

For API and MCP server providers, MCPay offers three integration paths: embed the SDK directly, route traffic through the no-code proxy, or list the server in the public registry for discoverability. Once integrated, pricing is configurable per call, per tool, or per token consumed, with dynamic pricing on the roadmap.

For AI clients and agents, MCPay offers a single account to access the full catalog of monetized tools. The pay-per-call model eliminates the overhead of managing multiple subscriptions across providers. Unused deposited funds can be withdrawn at any time, and MCPay charges no platform fee.

Metrics and Traction

As of the figures reported on the product site, MCPay has processed more than 100,000 transactions with a cumulative volume exceeding $30,000 across more than 2,500 users. The project is open source under the Apache 2.0 license, built primarily in TypeScript, and maintained in a pnpm monorepo on GitHub with 477 commits and 91 stars.

Team and Backing

MCPay was built by Luís Freitas (GitHub: microchipgnu), a developer based in Lisbon, Portugal, previously affiliated with Mintbase and BitteProtocol — two prominent projects in the NEAR and multi-chain ecosystem. He has a background in AI agent frameworks and markup languages for natural language programming.

The project lists Colosseum, Coinbase, Polygon, Vlayer, and ETHGlobal as backers and partners. Colosseum organizes Solana's flagship hackathon series, and its involvement underscores the Solana ecosystem's interest in the project. Coinbase's participation reflects its role as the originating author of the x402 specification that MCPay implements.

Solana Fit

MCPay's connection to Solana runs in several directions. Colosseum backing places the project within Solana's builder community and hackathon ecosystem. The explicit support for Solana mainnet and devnet as payment settlement networks means that Solana-native wallets and agents can participate in the x402 payment flow using USDC on Solana. As Solana continues to expand as a platform for DeFi applications and on-chain AI infrastructure, per-call micropayment primitives like MCPay become relevant infrastructure for both AI agents operating on Solana and for tool providers building services atop it.

The x402 protocol itself, with Coinbase as a co-promoter and Cloudflare adding native support in September 2025, had accumulated roughly $50 million in cumulative protocol volume as of early 2026 — providing a broader tailwind for any implementation including MCPay.

Status

MCPay is an active project. While the root domain mcpay.tech carries a temporary redirect to frames.ag (a successor product from the same creator, offering a broader AI model with integrated paid-data tooling using the same underlying payment infrastructure), the MCPay product itself remains live at v2.mcpay.tech with active documentation at docs.mcpay.tech. The codebase continues to receive commits on GitHub, with 477 commits across the main branch and active open issues and pull requests.