Use jscodeshift when the task is to apply a codemod across many JavaScript or TypeScript files, such as API migrations, naming rewrites, or framework upgrade cleanup. Invoke it instead of editing code manually or using a general coding assistant normally when you need one transform to run consistently over a large codebase with dry runs, parser control, and auditable output. The scope boundary is clear: this skill is about repeatable AST-driven codemod execution, not a generic library listing and not a broad JavaScript toolkit card.