diff --git a/.gemini/styleguide.md b/.gemini/styleguide.md
index 38598b09ff2..ac48ada5cd0 100644
--- a/.gemini/styleguide.md
+++ b/.gemini/styleguide.md
@@ -21,3 +21,13 @@ auto-formatter, for each language, as described in
 - PR descriptions should include the Pre-Review Checklist from
   [the PR template](https://github.com/flutter/packages/blob/main/.github/PULL_REQUEST_TEMPLATE.md),
   with all of the steps completed.
+
+## Review Agent Guidelines
+
+When providing a summary, the review agent must adhere to the following principles:
+- **Be Objective:** Focus on a neutral, descriptive summary of the changes. Avoid subjective value judgments
+  like "good," "bad," "positive," or "negative." The goal is to report what the code does, not to evaluate it.
+- **Use Code as the Source of Truth:** Base all summaries on the code diff. Do not trust or rephrase the PR
+  description, which may be outdated or inaccurate. A summary must reflect the actual changes in the code.
+- **Be Concise:** Generate summaries that are brief and to the point. Focus on the most significant changes,
+  and avoid unnecessary details or verbose explanations. This ensures the feedback is easy to scan and understand.