I was impressed with Claude Sonnet the other day - gave it a photo of my credit card bill (3 photos actually - long bill) and asked it to break it down by recurring categories, counting anything non-recurring as "other". It realized without being asked that a program was needed, and wrote/ran it to give me what I asked for.
In general it's "tool use" where the model's system prompt tells it to use certain tools for certain tasks, and having been trained to follow instructions, it does so!
