Zod 4 vs Valibot vs ArkType as MCP tool schemas (I timed them)

I wrote this (my own blog). I needed a schema lib for MCP tool inputs and kept seeing Zod vs Valibot vs ArkType takes with no numbers, so I timed the same schemas on Node 24 with tinybench and checked bundle size with esbuild. Numbers and the MCP wiring are in the post. Short version: Valibot won the hot path for the shapes I use, ArkType was close, Zod 4 was fine but heavier. Bundle size mattered more than I expected once the schemas sat behind an MCP server. Curious what people actually ship for tool schemas in production — Zod by default, or something lighter?