We cut Claude's token usage 79% by redesigning our CLI for agents (opens in new tab)

co-founder of Infracost here, we launched Infracost on HN five years ago, when the CLI just generated cost estimates for Terraform. Earlier this year we were scoping a 1.0 release: the CLI would stop being just a cost-estimation tool and start surfacing the issues behind the costs: previous-generation instances, policy violations, the kinds of issues a thorough PR review would catch.

Then agent traffic started showing up, and it became clear the 1.0 scope was the right idea aimed at the wrong caller. A human reviewer reads a PR comment; an agent runs `infracost inspect --filter` ... and gets the same insight as a tabular row it can pipe into the next step. So we decided to skip our planned 1.0 release and go for 2.0, where we treated agents as a first-class citizen user of the CLI.

Along the way we picked up some interesting lessons on optimizing user token usage when designing a CLI, and we want to share them with the HN community since other CLI builders might benefit.

Designing interfaces specifically for agents (M2M DX) is a fascinating shift from traditional human-centric CLI design. We're moving from a world where "pretty" output and progress bars mattered to a world where raw, structured density is the goal. A 79% reduction is massive, but I wonder if we’ll see a new type of "Agent-Optimized" protocol emerge that completely bypasses the text-heavy nature of current CLIs. The overhead of an LLM trying to parse "human" terminal output is essentially a tax on every call.