MCP defines how AI hosts connect to tool servers. By default MCP servers are free; pairing them with x402 lets each tool call require an on-chain micropayment, which gives spam resistance and direct monetisation without API keys.
Free MCP for community tools, x402-gated MCP for anything you'd otherwise gate behind an API key. The two coexist in the same MCP host.
Expose read-only metadata for free, gate compute-heavy or data-heavy tools behind x402. The MCP tool descriptor advertises the price.