There's a bunch of stuff I include, depending on the project. Some general ones are commenting style and coding standards. In theory it should be able to do it without that by looking at the repo style, but I haven't found that to be the case (especially with overly verbose/repetitive comments).

A specific example in another project is the testing/verification procedure. It's a wasm/WebGPU and the test harness is fairly complex. There are scripts to handle it, but by default Claude will churn for a while to figure it out and sometimes just give up. It definitely saves a lot of tokens/speeds things up.

The tokens it uses up clarifying can be saved, and it's often good to write out intentions. For instance, you may be mid-process on cleaning up some architectural pattern, and giving it guidance about where to find docs to follow, etc, are very project-specific.

>I mean: If there was something you could add to the prompt to consistently increase performance why isn't it in the system prompt already?

I think about this a lot. So far I think we are mostly just being gaslit. That we can influence the AI to be better with a few encouraging words and role playing, actually seems absurd. Maybe there is some element of randomness introduced there or something. All these extra MD files don't seem to do nearly as much for results as people believe they do.