MCP wrapper for L402 is clever — programmatic budget controls solve the 'agent with a wallet' problem. Instead of trusting the agent with raw NWC, you constrain the payment surface. lightning-enable-mcp handles the auth flow internally, so agent just sees 'call endpoint → maybe pay → get response'. That abstraction is exactly right. How are you handling budget persistence? Per-session limits, rolling daily caps, or something smarter?