Second Opinion MCP

An MCP server that lets your AI coding assistant consult a different, strong coding assistant, when it needs a fresh perspective.

It delegates to locally installed CLI agent harnesses, enabling the subagents to use full power of their tooling: search, explore, inspect e.t.c.

When your agent is stuck or you want a sanity check, just say "ask gemini", "ask codex", "ask claude", or "ask kilo" and it queries the other model with the relevant files as context.

History

Originally vibed in node.js ; then rewriten into rust to save on memory (and tokens!)

Prerequisites

Install the CLI tools you want to use:

1. Gemini CLI
2. Codex CLI
3. Claude Code
4. Kilocode CLI

Configure each CLI with your preferred billing method. Subscription or API key is handled by the CLI itself — this server never touches API keys.

Quick start

Clone, then build:

cargo build --release

Register the MCP server:

# claude mcp add --scope user grey-so -- npx -y grey-so
claude mcp add --scope user grey-rso -- $(pwd)/rust/target/release/grey-rso
gemini mcp add --scope user grey-rso $(pwd)/rust/target/release/grey-rso
codex mcp add grey-rso -- $(pwd)/rust/target/release/grey-rso
kilo mcp add grey-rso -- $(pwd)/rust/target/release/grey-rso  
# The above often fails, await better documentation from kilo. For now, edit `nano ~/.config/kilo/opencode.json` instead.

Test it:

gemini -p -y "testing: use the consult tool and ask all models - what is the capital of Paris?"
codex exec "testing: use the consult tool and ask all models - what is the capital of Paris?"
kilo run "testing: use the consult tool and ask all models - what is the capital of Paris?"
ANTHROPIC_API_KEY=  claude --allowedTools mcp__grey-rso__consult -p "use the consult tool and ask all models, in parallel: what is the capital of Paris?"

How it works

The MCP tool exposes a single consult tool. The caller picks one of four short aliases — gemini, claude, codex, kilo — and the server maps that alias to an actual model name via a config file, then shells out to the corresponding CLI.

This keeps the MCP interface minimal and spends as little of your precious tokens as possible, when not used.

Example use

> Still getting this error after your fix. Ask gemini.

  Let me consult Gemini about the Neovim treesitter API changes:

  grey-so:consult (MCP)(prompt: "Neovim plugin broken due to treesitter
                                API changes...", files: ["lua/testonly.lua"],
                                model: "gemini")
   The issue is that (...)

Further reading

See DETAILS.md for slash command examples, skill setup, and development instructions.