I just added a short chapter on using the Anthropic completion API to my Common Lisp book. Here is a link to the start of the new material https://leanpub.com/lovinglisp/read#leanpub-auto-using-the-anthropic-claude-llm-completion-api
If you have been using OpenAI’s APIs from Common Lisp and want to try using Anthropic, this new material should save you a few minutes work getting setup.