| name | gemini-prompting |
| description | Gemini model prompting guide for effective task delegation from Claude Code |
| user-invocable | false |
Gemini Prompting Guide
When to Use
Use this skill only to shape the prompt text before forwarding it to the gemini-companion runtime. Do not use it to do independent work, inspect the repository, or draft solutions.
Model Selection
The default model is auto-gemini-3. Only override it when the action type has a clear reason to use a different tier.
Action-based routing
| Action type | Examples | Recommended model |
|---|
| Deep reasoning / root-cause diagnosis | Multi-file bug investigation, security audit, architecture review | pro (gemini-3.1-pro-preview) |
| Complex implementation | Refactor across many files, design a new subsystem, write an algorithm | pro (gemini-3.1-pro-preview) |
| Standard code tasks | Fix a specific bug, implement a well-scoped feature, write tests | auto-gemini-3 (default — omit --model) |
| Code review / adversarial review | /gemini:review, /gemini:adversarial-review | auto-gemini-3 (default — omit --model) |
| Quick lookup / simple edit | One-liner fix, rename, trivial grep-and-replace | flash (gemini-3-flash-preview) |
| Latency-critical / high-volume | CI pre-check, tight feedback loop, batch summarisation | flash-lite (gemini-3.1-flash-lite-preview) |
| Production-stable (no previews) | Workloads that must avoid preview model churn | auto-gemini-2.5 |
Decision rule
- User explicitly named a model → use it, pass as
--model <name>.
- Task involves deep reasoning, complex multi-file implementation, or security analysis → use
--model pro.
- Task is a standard code fix, feature, or review → omit
--model (defaults to auto-gemini-3).
- User asked for speed or the task is trivially small → use
--model flash or --model flash-lite.
- User requires preview-free stability → use
--model auto-gemini-2.5.
Gemini Model Characteristics
- Long context: Gemini models handle up to 1M tokens of context. Lean into providing full file contents rather than snippets.
- System instructions: Gemini's primary steering mechanism. Place behavioral constraints, output format requirements, and role definitions in system instruction blocks.
- Thinking: Gemini models support configurable thinking budgets. Use
--thinking-budget for complex reasoning tasks.
- Grounding: Gemini can use Google Search for grounding. For tasks requiring up-to-date information, mention this in the prompt.
- Structured output: Request JSON output by describing the schema in the prompt. Gemini follows schema instructions well when given clear examples.
Prompt Structure
Use XML tags to structure prompts for clarity:
<role>
Define the persona and operating stance.
</role>
<task>
State what needs to be done. Be specific about inputs and expected outputs.
</task>
<context>
Provide repository context, file contents, error messages, or other relevant information.
</context>
<constraints>
List hard boundaries: what NOT to do, scope limits, safety rules.
</constraints>
<output_contract>
Define the exact output shape. Use JSON schema descriptions or examples.
</output_contract>
Key Principles
- Be specific, not vague: "Fix the null pointer in
auth.go:142" beats "Fix the bug".
- Include output contracts: Always specify what the response should look like.
- Provide full context: Gemini handles long context well — give it complete files, not snippets.
- Use system instructions for behavior: Role, tone, constraints go in system instruction blocks.
- One task per prompt: Don't mix unrelated jobs. Split into separate runs.
- Include verification steps: Ask Gemini to verify its own work before finalizing.
References
