bundler_mcp is a server based on the Model Context Protocol (MCP), designed to let AI agents query information about dependencies in a Ruby project's Gemfile, including source code and metadata. It is built using fast-mcp.
Main capabilities: The server provides two tools for AI agents: first, listing all bundled Ruby gems, including their installation paths and top-level documentation locations (such as README and CHANGELOG); second, retrieving detailed information about a specific gem, including installation path, top-level documentation locations, and source code file locations.
Usage: Install the gem and add it to the application's Gemfile by running the command. Generate a binstub. Configure the client to execute the binstub; examples are provided for Claude and Cursor, including a basic example (mcp.json) and an example with logging and an explicit Gemfile. Regarding environment variables: BUNDLE_GEMFILE is used by Bundler to locate the Gemfile, and is usually not needed if the binstub method is used; BUNDLER_MCP_LOG_FILE specifies the log file path to facilitate troubleshooting (no logging by default). For testing, you can use MCP Inspector to test the server directly.
Use cases: Suitable for development scenarios where AI agents need to query gem dependency information in Ruby projects.
Limitations: The material does not provide information about charges, pricing, performance, or specific usage restrictions.
