Gemini Skill Guide

When to Use Gemini

• Code Review: Comprehensive code reviews across multiple files
• Plan Review: Analyzing architectural plans, technical specifications, or project roadmaps
• Big Context Processing: Tasks requiring >200k tokens of context (entire codebases, documentation sets)
• Multi-file Analysis: Understanding relationships and patterns across many files

Running a Task

1. Ask the user (via AskUserQuestion) which model to use in a single prompt. Latest models (all support thinking):

   • gemini-2.5-pro (state-of-the-art, best for complex reasoning in code/math/STEM)
   • gemini-2.5-flash (best price-performance, recommended for most tasks)
   • gemini-2.5-flash-lite (fastest, most cost-efficient, high throughput)

2. Select the approval mode based on the task:

   • default: Prompt for approval (safest, for read-only analysis)
   • auto_edit: Auto-approve edit tools only (for code reviews with suggestions)
   • yolo: Auto-approve all tools (for trusted automated changes)

3. Assemble the command with appropriate options:

   • -m, --model <MODEL> - Model selection
   • --approval-mode <default|auto_edit|yolo> - Control tool approval
   • -y, --yolo - Alternative to --approval-mode yolo
   • -i, --prompt-interactive "prompt" - Execute prompt and continue interactively
   • --include-directories <DIR> - Additional directories to include in workspace
   • -s, --sandbox - Run in sandbox mode for isolation

4. Default to --approval-mode default for read-only analysis tasks unless edits are necessary.

5. Run the command and capture the output. For non-interactive mode, use positional arguments:

   gemini -m gemini-2.5-flash --approval-mode default "Review this codebase for security issues"
   

6. For interactive sessions with an initial prompt:

   gemini -m gemini-2.5-flash -i "Review the authentication system" --approval-mode auto_edit
   

7. After Gemini completes, inform the user: "The Gemini analysis is complete. You can start a new Gemini session for follow-up analysis or continue exploring the findings."

Quick Reference

Use case	Approval mode	Key flags
Code review (read-only)	default	-m gemini-2.5-flash --approval-mode default
Code review with suggestions	auto_edit	-m gemini-2.5-flash --approval-mode auto_edit
Big context analysis	default	-m gemini-2.5-pro --approval-mode default
Plan/architecture review	default	-m gemini-2.5-pro --approval-mode default
Automated refactoring	yolo or -y	-m gemini-2.5-flash --approval-mode yolo
High-throughput tasks	default	-m gemini-2.5-flash-lite --approval-mode default
Multi-directory analysis	Depends on task	--include-directories <DIR1> --include-directories <DIR2>
Interactive with initial prompt	Match task needs	-i "prompt" --approval-mode <mode>

Model Selection Guide

Model	Best for	Context window
gemini-2.5-pro	State-of-the-art reasoning, complex code/math/STEM problems	1M input / 65k output
gemini-2.5-flash	Best price-performance, large-scale processing, agentic tasks	1M input / 65k output
gemini-2.5-flash-lite	Fastest & most cost-efficient, high throughput	1M input / 65k output

All Gemini 2.5 models support thinking capabilities for enhanced reasoning and accuracy.

Common Use Cases

Code Review

gemini -m gemini-2.5-flash --approval-mode default \
  "Perform a comprehensive code review focusing on:
   1. Security vulnerabilities
   2. Performance issues
   3. Code quality and maintainability
   4. Best practices violations"

Plan Review

gemini -m gemini-2.5-pro --approval-mode default \
  "Review this architectural plan for:
   1. Scalability concerns
   2. Missing components
   3. Integration challenges
   4. Alternative approaches"

Big Context Analysis

gemini -m gemini-2.5-pro --approval-mode default \
  "Analyze the entire codebase to understand:
   1. Overall architecture
   2. Key patterns and conventions
   3. Potential technical debt
   4. Refactoring opportunities"

Following Up

• Gemini CLI sessions are typically one-shot or interactive. Unlike Codex, there's no built-in resume functionality.
• For follow-up analysis, start a new Gemini session with context from previous findings.
• When proposing follow-up actions, restate the chosen model and approval mode.
• Use AskUserQuestion after each Gemini command to confirm next steps or gather clarifications.

Error Handling

• Stop and report failures whenever gemini --version or a Gemini command exits non-zero.
• Request direction before retrying failed commands.
• Before using high-impact flags (--approval-mode yolo, -y, --sandbox), ask the user for permission using AskUserQuestion unless already granted.
• When output includes warnings or partial results, summarize them and ask how to adjust using AskUserQuestion.

Tips for Large Context Processing

1. Be specific: Provide clear, structured prompts for what to analyze
2. Use include-directories: Explicitly specify all relevant directories
3. Choose the right model:
   • Use gemini-2.5-pro for complex reasoning and maximum analysis depth
   • Use gemini-2.5-flash for most code reviews (best price-performance)
   • Use gemini-2.5-flash-lite for high-volume, fast processing
4. Leverage thinking capabilities: All 2.5 models have built-in thinking for better reasoning
5. Break down complex tasks: Even with large context, structured analysis is more effective
6. Save findings: Ask Gemini to output structured reports that can be saved for reference