Function is_plausible_tool_name 

pub fn is_plausible_tool_name(name: &str) -> bool

A name the note may quote: what tool wire names look like (ToolRegistry exposes [A-Za-z0-9_-]{1,128}), plus . and : for runtime-style names. The name comes straight from the model’s call, so anything else (a backtick, a newline, an overlong string) is never copied into a user-role message: it reads UNRECOGNISED_TOOL.