Braintrust for Cursor

Connect Cursor to Braintrust, giving Cursor's AI assistant access to your projects, experiments, and logs via MCP.

This repo provides two ways to install:

• Cursor Plugin — lightweight MCP config, installed via the Cursor Marketplace
• VS Code Extension — auto-registers the MCP server on startup via the Cursor Extension API

Prerequisites

• Cursor
• A Braintrust API key

Install as Plugin

Install from the Cursor Marketplace:

1. Open Cursor
2. Run /add-plugin and search for "Braintrust", or install from cursor.com/marketplace
3. Set the BRAINTRUST_API_KEY environment variable (see Setup)

The plugin adds the Braintrust MCP server to your Cursor environment. No build step required.

Install as Extension

Install from the Cursor extension panel:

1. Open Cursor
2. Go to Extensions (Cmd+Shift+X / Ctrl+Shift+X)
3. Search for "Braintrust"
4. Click Install

The extension automatically registers the Braintrust MCP server when Cursor starts.

Setup

Set your API key

Both the plugin and extension read your API key from the BRAINTRUST_API_KEY environment variable. Set this before launching Cursor.

macOS / Linux

Add to your shell profile (~/.bashrc, ~/.zshrc, etc.):

export BRAINTRUST_API_KEY="your-api-key-here"

Then restart your terminal and Cursor.

Windows

Set the environment variable via System Properties > Environment Variables, or in PowerShell:

[Environment]::SetEnvironmentVariable("BRAINTRUST_API_KEY", "your-api-key-here", "User")

Then restart PowerShell and Cursor.

Troubleshooting

"BRAINTRUST_API_KEY is not set"

• Verify the variable is set: echo $BRAINTRUST_API_KEY (macOS/Linux) or echo %BRAINTRUST_API_KEY% (Windows)
• Cursor must be restarted after setting environment variables
• On macOS, launching Cursor from Spotlight/Dock may not inherit shell variables — launch from terminal instead

Extension doesn't seem to work

• The extension only works in Cursor, not vanilla VS Code
• Ensure you're running a recent version of Cursor that supports the MCP Extension API

Contributing

See CONTRIBUTING.md for development setup and build instructions.

License

MIT