Beliefs about the performance of new technologies strongly condition their usage. Among new technologies, artificial intelligence (AI)—and in particular LLMs—stand out because they can be used for extremely diverse sets of tasks. This versatility, however, complicates the problem of learning about AI capabilities, especially since the technological frontier created by AI is often "jagged": among seemingly similar tasks, AI can vastly out-perform humans on some, yet under-perform on others. Inaccurate perceptions of performance could lead to productivity losses, if AI is used for tasks on which it performs poorly.