Kontra

The best ideas are forged under challenge. People know this: we argue, we push back, and what survives is sharper. An AI chat skips that step. It thinks on its own and tends to agree with you. Kontra puts the challenge back in. The moment you prompt, one or more AI debaters take the other side and argue it out with your assistant, so the answer you get has already been tested.

It runs as an MCP server. You bring your own API keys.

How it works

1. You turn on kontra mode and ask a question.
2. Your assistant writes its position and sends it to the debaters.
3. Each debater replies in character with a stance and either "keep going" or "settled".
4. After each round your assistant recaps the points raised, answers them, and runs another round, until the debate settles.
5. Your assistant replies with a short, structured rundown: the positions and their strongest arguments, where the debate lands, and a recommendation.

The debate runs for as many rounds as it needs. A round limit stops it from running forever.

Install

Easiest: one click (Claude Desktop)

No Node, no config files, no terminal.

1. Download kontra.mcpb from the latest release.
2. Open Claude Desktop, go to Settings, then Extensions.
3. Drag kontra.mcpb into the window (or double-click the file).
4. Paste your API key into the box when asked, and turn it on.

Claude Desktop bundles everything and stores your key in your operating system's secure storage.

Other MCP clients (Claude Code, Cursor, and more)

Kontra is a standard MCP server, so it works in any MCP client. You need Node 18 or newer. Add this server entry to the client's MCP config, then restart the client:

{
  "mcpServers": {
    "kontra": {
      "command": "npx",
      "args": ["-y", "mcp-kontra"],
      "env": { "ANTHROPIC_API_KEY": "sk-ant-..." }
    }
  }
}

Where each client keeps that config:

Client	Config
Claude Code	.mcp.json in your project, or run claude mcp add
Cursor	.cursor/mcp.json
Claude Desktop (manual)	Settings, then Developer, then Edit Config
Windsurf, Cline, and others	that client's MCP settings file

Some clients (such as VS Code's built-in MCP support) use a servers key instead of mcpServers. The command, args, and env are the same.

You start with one debater: a ruthless contrarian on Claude Opus 4.8.

Your API keys

Kontra never takes a key through the chat. It reads keys only from environment variables, set one of two ways:

• One-click install: type the key into the secure form. It is stored by your operating system, not in a file.
• Other clients: put the key in the env block of the server entry above.

A few notes:

• You only need a key for the providers your debaters actually use. By default that is just Anthropic (Claude), so you are asked for one key, not three.
• If a key is missing, Kontra tells your assistant which single key to add, and your assistant asks you for it in the chat.
• Do not commit a config file that contains a real key.
• After adding or changing a key, restart the client.

Use it

Say "kontra mode on" and ask a question. To change the debate, just ask in plain words, and your setup is saved until you change it. You can set the personas, the number of debaters (up to 5), each debater's provider and model, and the round limit (up to 12).

Examples

Real prompts, from quick gut-checks to bigger calls. Use the default challenger, or set up your own panel.

Product and engineering

kontra mode on. Planning to fix the slow dashboard with a 60-second cache. Before I build it, what am I missing?

kontra mode on. Going to mark this flaky test as skipped so CI stops blocking the team. Talk me out of it.

Commercial

kontra mode on. A customer about to churn asked for 20% off to stay, and I want to say yes. Argue the other side.

kontra mode on. Have a skeptical CFO and a growth-minded sales lead argue it out: should we offer net-60 terms to land a big deal?

Personal

kontra mode on. About to sign a 12-month lease at 40% of my take-home. Push back before I commit.

kontra mode on. Here's the message I drafted to a friend who keeps cancelling on me. What will I wish I'd changed?

Providers

Pick any debater's provider. Set the matching key (in the one-click form, or as an env var).

Provider	API key	Example models
anthropic	ANTHROPIC_API_KEY	claude-opus-4-8 (default), claude-sonnet-4-6
openai	OPENAI_API_KEY	gpt-5.5 (default), gpt-5.4-mini
google	GEMINI_API_KEY	gemini-3.5-flash (default), gemini-2.5-pro

Any model the provider offers works. If you name one that does not exist, Kontra tells you so you can fix it.

Tools

• debate_status: shows your saved debaters, models, round limit, and which keys are set.
• configure_debate: changes and saves the setup.
• challenge: runs one round of debate.

Your assistant calls these for you. You just talk to it.

Where settings are saved

Kontra saves your setup to ~/.kontra/config.json. Point it somewhere else with the KONTRA_CONFIG environment variable.

Develop

git clone https://github.com/a1ex-bb/kontra.git
cd kontra
npm install
npm run build      # compile TypeScript to dist/
npm run bundle     # build kontra.mcpb for one-click install

Try the tools in a browser with the MCP Inspector. Set the key for whichever providers you want to exercise. Anthropic alone is enough for the default debater; add the others only if you configure debaters on them:

ANTHROPIC_API_KEY=sk-ant-... npm run inspect
# add OPENAI_API_KEY=... and/or GEMINI_API_KEY=... too if your debaters use them

License

MIT