Function changes 

pub fn changes(tool: &str, input: &Value) -> bool

Whether a tool call changes state: an edit tool (Edit, Write, MultiEdit, NotebookEdit), or a Bash command any part of which is not read-only (READ_ONLY, read-only git), redirects output into a file, or edits in place (sed -i, find -delete/-exec). Other tools (Read, Grep, Glob, …) read.