Unit tests check that an agent's code runs, so a one-line change to its instruction can make its answers worse while the tests keep passing.

Last year we covered this in the Kaggle AI Agents Intensive with Google, in Prototype to Production , the Day 5 whitepaper. It says no agent version should reach users until it passes an automated evaluation, and Agents CLI , the command-line tool for building, evaluating, and deploying agents on Google Cloud, turns the pre-merge part of that rule into one setting in v1.13.0. In this post I add it to a fresh project and then to the project's CI, the continuous integration checks that run on every pull request.

Figure 1. The eval passes or fails the pull request check through the exit code your CI already reads.

Why agents need a different gate

An agent decides what to do on each request, so you grade its replies and its tool calls (the functions it runs, such as a weather lookup) on a set of known cases.…