Actually, I just realized that it's not really possible to fix the error messages for built-in methods. The problem is that Argument Clinic does not know whether a function or method is being handled. For example, there is no indication at all that this is a method (note that the name "list.insert" might refer to a function "insert" inside a module called "list" or a method "insert" or a class "list"): /*[clinic input] list.insert index: Py_ssize_t object: object / Insert object before index. [clinic start generated code]*/