MCP Tool Hooks in Claude Code

Your hooks run shell scripts. Every time a hook needs to call an MCP server, it spawns a subprocess, wires up transport, handles auth, parses the response, and formats JSON back to stdout. For a security check that fires on every file write, that overhead adds up fast. As of Claude Code v2.1.118, there is a cleaner path. Hooks have a new type that calls MCP tools directly. No subprocess. The MCP server is already running. The hook calls straight into its RPC connection. Add this to .claude/setti