L402's (1) macaroon-based authentication would fit naturally with MCP's server architecture. Since MCP servers already define their capabilities and handle tool-specific requests, adding L402 token validation would be straightforward - the server could check macaroon capabilities before executing tool requests. This could enable per-tool pricing and usage limits while maintaining MCP's clean separation between transport and tool implementation. The Aperture proxy could sit in front of MCP servers to handle the Lightning payment flow, making it relatively simple to monetize existing MCP tool servers without significant modifications to their core functionality.

(1) https://github.com/lightninglabs/aperture