> we have a custom .yaml spec for data pipelines in our product and the agent follows it as well as anything in the training data.

Doesn't this end up being way more expensive, because you don't pay for model parameter activations but for the tokens in/out, meaning that anything not in the training data (and therefore, the model) will cost you. I could make Opus use a new language I came up with if I wanted to and it'd do an okay job with enough information... but it'd be more expensive and wasteful than just telling it to write the same algorithms in Python, and possibly a bit more error prone. Same with frameworks and libraries.