Preflight before paying any x402 tool (ok|caution|avoid + history). 1 free/wallet; then $0.01 Base.
Streamable HTTP
https://x402check.dev/mcpclaude mcp add --transport http x402check https://x402check.dev/mcpx402check-mcp · npm 0.1.6 · stdio
claude mcp add --transport stdio x402check -- npx -y x402check-mcp@0.1.6