Boxcars is a Ruby framework for building LLM-powered systems with less cognitive load, especially for Ruby and Rails teams. It provides tool composability through Boxcar objects that can be reused across assistants, jobs, and services. The framework supports multiple orchestration modes including legacy ReAct and native provider tool calling, integrates with MCP servers over stdio, and offers data-aware workflows combining SQL, ActiveRecord, vector search, and API-backed tools. Provider flexibility is built in with support for OpenAI, Anthropic, Groq, Gemini, Ollama, and Perplexity through shared engine patterns.