Behavioral Evals Agent Skill
Guidance for creating, running, fixing, and promoting behavioral evaluations. Use when verifying agent decision logic, debugging failures, debugging prompt steering, or adding workspace regression tests.
Install
one command, takes just this skill from the repositorynpx skills add https://github.com/google-gemini/gemini-cli --skill behavioral-evalsWhat comes with it
15 723 bytes besides the instructionThe instruction itself
8 sections, as written by the authorBehavioral Evals
Overview
Behavioral evaluations (evals) are tests that validate the agent's decision-making (e.g., tool choice) rather than pure functionality. They are critical for verifying prompt changes, debugging steerability, and preventing regressions.
> [!NOTE]
> Single Source of Truth: For core concepts, policies, running tests, and general best practices, always refer to evals/README.md.
🔄 Workflow Decision Tree
- Does a prompt/tool change need validation?
- *No* -> Normal integration tests.
- *Yes* -> Continue below.
- Is it UI/Interaction heavy?
- *Yes* -> Use
appEvalTest(AppRig). See creating.md. - *No* -> Use
evalTest(TestRig). See creating.md. - Is it a new test?
- *Yes* -> Set policy to
USUALLY_PASSES. - *No* ->
ALWAYS_PASSES(locks in regression). - Are you fixing a failure or promoting a test?
- *Fixing* -> See fixing.md.
- *Promoting* -> See promoting.md.
📋 Quick Checklist
1. Setup Workspace
Seed the workspace with necessary files using the files object to simulate a realistic scenario (e.g., NodeJS project with package.json).
- *Details in creating.md*
2. Write Assertions
Audit agent decisions using rig.setBreakpoint() (AppRig only) or index verification on rig.readToolLogs().
- *Details in creating.md*
3. Verify
Run single tests locally with Vitest. Confirm stability locally before relying on CI workflows.
- *See evals/README.md for running commands.*
📦 Bundled Resources
Detailed procedural guides:
- creating.md: Assertion strategies, Rig selection, Mock MCPs.
- fixing.md: Step-by-step automated investigation, architecture diagnosis guidelines.
- promoting.md: Candidate identification criteria and threshold guidelines.
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How to use it
Take google-gemini/behavioral-evals from the repository into ~/.claude/skills for personal
use, or into .claude/skills inside a project.
The agent identifies a skill by the name field in its header. Two skills with the
same name cannot sit side by side — one of them will be ignored.