In Lisp, side effects—including API calls—are handled through standard function calls that, when evaluated, interact with the external world. While Lisp expressions are evaluated uniformly (with both pure and effectful functions treated as expressions), the language allows programmers to deliberately introduce side effects. There’s no enforced separation like in languages with a strict purity model; instead, functions that perform operations such as API calls simply produce effects as part of their execution, and it is up to the programmer to manage and order these operations as needed.