This skill is for Claude only. Codex and Gemini CLI should not invoke it.

Second Opinions

Delegate tasks to OpenAI Codex (MCP) and/or Google Gemini (CLI) for independent perspectives from different model families. Works for code review, plan evaluation, doc editing, codebase analysis, or any arbitrary task.

Modes: both (default), codex, gemini

When To Use

Code review before committing, opening a PR, or merging
Plan or architecture review from multiple perspectives
Documentation review or content editing
Codebase analysis (patterns, race conditions, dead code)
Any task benefiting from parallel exploration by external models

Scope

Skip for trivial tasks you can verify directly
Skip when the user asked for your own judgment only
Exclude secrets, credentials, and tokens from prompts

User Instructions

Follow any user instructions below. They override the standard workflow when conflicts arise.

<user_instructions> $ARGUMENTS </user_instructions>

Workflow

1. Gather Context

Use AskUserQuestion to collect parameters. Skip questions whose answers are obvious from user arguments. Combine into one call (max 4 questions).

Tool (always ask unless specified):

header: "Tool"
question: "Which model should run this?"
options:
  - "Both Codex and Gemini (Recommended)" -> parallel dispatch
  - "Codex only"
  - "Gemini only"

Task type (always ask unless clear from arguments):

header: "Task type"
question: "What kind of task?"
options:
  - "Code review (diff-based)"
  - "Plan or architecture review"
  - "Documentation or content review"
  - "Custom task"

Focus (skip for custom tasks where the user already specified intent):

header: "Focus"
question: "Any specific focus?"
options:
  - "General review"
  - "Security & auth"
  - "Performance"
  - "Correctness & edge cases"

Diff scope (only for code review):

header: "Diff scope"
question: "What should be reviewed?"
options:
  - "Uncommitted changes"  -> git diff HEAD + untracked
  - "Branch diff vs main"  -> git diff <branch>...HEAD
  - "Specific commit"      -> follow up for SHA

2. Build Material

Gather content based on task type:

Task type	Material to gather
Code review	Git diff per selected scope. Auto-detect default branch. Show `--stat`. Warn if >2000 lines or empty.
Plan/architecture	Extract plan from conversation context. Read any referenced files. If no plan in context, ask the user.
Documentation	Read target files. Warn if >2000 lines total.
Custom task	Use user instructions as the task definition. Read any referenced files or directories.

Auto-detect default branch for code reviews:

git symbolic-ref refs/remotes/origin/HEAD 2>/dev/null | sed 's@^refs/remotes/origin/@@' || echo main

3. Construct & Dispatch

Prompt structure — use XML tags for unambiguous parsing. Put long content first, instructions after (per Anthropic long-context best practices):

<material>
[The diff, plan, document, codebase excerpt, or task input — long content goes first]
</material>

<context>
[Project conventions from CLAUDE.md, if it exists]
</context>

<role>
[Role appropriate to the task — e.g., independent code reviewer, architecture evaluator, technical editor]
</role>

<task>
[What to do — review, analyze, evaluate, rewrite, etc.]
</task>

<focus>
[Focus area if specified]
</focus>

<output_format>
Structure your response as:
1. Critical issues (blocking)
2. Important concerns (should address)
3. Minor suggestions (nice to have)
4. What's done well

End with a clear verdict and confidence score (0-1).
</output_format>

Adapt <role>, <task>, and <output_format> to the task type. For code reviews, use the OpenAI cookbook prompt from codex.md. For custom tasks, translate the user's intent directly.

Project context: If CLAUDE.md exists in the repo root, always include it so reviewers check against project conventions.

See references/codex.md for Codex MCP prompt patterns and invocation. See references/gemini.md for Gemini CLI invocation patterns.

Dispatch rules:

When running both tools, issue mcp__codex__codex and Bash(gemini ...) calls in a single message for parallel execution.
Dispatch directly without pre-checking tool availability. If a tool fails, run only the available one.

Iterative mode (for plans/architecture, or when explicitly requested):

Dispatch initial review
If reviewer returns significant concerns, revise the material based on feedback
Re-submit using mcp__codex__codex-reply (with threadId) or a fresh gemini call including revision context
Max 3 rounds to prevent loops

4. Present Results

Both tools:

## Codex Findings
<findings>

## Gemini Findings
<findings>

## Synthesis
- **Agreements**: Where both models align
- **Divergences**: Where they disagree and your assessment of who's right
- **Action items**: Prioritized changes to consider

Single tool: Present findings with your assessment of which items are valid vs uncertain.

Error Handling

Error	Action
`mcp__codex__codex` unavailable	Run Gemini only
`gemini: command not found`	Run Codex only
Both unavailable	Stop and inform the user
Gemini extension missing	Install: `gemini extensions install <github-url>` (see gemini reference)
Empty diff / no content	Stop: nothing to review
Timeout	Suggest narrowing scope
One tool fails	Present the other's results, note the failure

Examples

Code review (both tools):

User: /second-opinions
Agent: [asks tool, task type, focus, diff scope]
User: "Both", "Code review", "Security", "Branch diff"
Agent: [shows diff --stat, dispatches both in parallel]
Agent: [presents synthesis with agreements/divergences]

Plan review (iterative, single tool):

User: /second-opinions review my migration plan with codex
Agent: [asks focus] -> "Correctness & edge cases"
Agent: [extracts plan, dispatches to Codex]
Codex: [returns concerns]
Agent: [revises plan, re-submits via codex-reply]
Codex: [approves revised plan]
Agent: [presents final result]

Custom task:

User: /second-opinions have gemini analyze src/auth/ for race conditions
Agent: [dispatches Gemini with direct file reading]
Agent: [presents findings with assessment]