Example: read this log file and extract XYZ from it and show me a table of the results. Instead of having the agent read in the whole log file into the context and try to process it with raw LLM attention, you can get it to read in a sample and then write a script to process the whole thing. This works particularly well when you want to do something with math, like compute a mean or a median. LLMs are bad at doing math on their own, and good at writing scripts to do math for them.
A lot of interesting techniques become possible when you have an agent that can write quick scripts or CLI tools for you, on the fly, and run them as well.