Alternatives to Marvin

Google's open-source framework for building agentic AI apps in JS, Go, Python & Dart.

Open-source Python framework turning messy text into typed, queryable Semantic DataFrames

Guidance is an open-source Python library for constrained LLM generation with regex, CFG, and native control flow.

Open-source LLM that turns natural language into API calls for tool-using agents

Open-source streaming-first toolkit that turns AI agent output into interactive UI, not JSON.

Open-source MCP testing & app framework for building ChatGPT Apps and Claude Connectors.

Open-source Python & TypeScript SDK for building production-grade AI agents with hooks, model routing, and cost controls.

EffGen is a Python framework for building AI agents on small language models, run locally or through any OpenAI-compatible server.

Open-source DDD pipeline framework for building custom SDLC LLM copilots.

Vercel AI SDK is an open-source TypeScript toolkit for building AI apps with 100+ models, real-time streaming, fallbacks, and agents

Compress AI agent context by up to 90% with a local, open-source MCP server.

Open Harness is an open-source TypeScript SDK for building Claude Code-style agent harnesses with stateless primitives and composable middleware.

Open-source Swift package wrapping the OpenAI API with async/await and Combine.

Open-source Java library for building LLM-powered apps with a unified API

Open-source React toolkit for generative UI — let LLM agents render your own components

Open-source Rust CLI that filters command output before it hits your LLM

Open-source React chat UI components for LLM interfaces

Mirascope: Build LLM apps with decorators, observability, and full control.

Python library for guaranteed valid structured outputs from LLMs using FSM constrained decoding

Pydantic AI is the Python AI SDK for typed agents, realtime voice, image generation, and embeddings — every model a string swap away.

Free GitHub repo of OpenAI API code examples, guides, and Jupyter notebooks.

Go-native LLM framework by ByteDance for building production-grade AI applications.

Extra-small OpenAI-compatible AI SDK for JS — 40x smaller installs.

Python library for reliable, testable LLM output

The frontend stack for agentic user experience — drop-in chat, generative UI, and shared state for React apps on any AG-UI backend

Type-safe programming language for building AI agents with compile-time guarantees.

LangChain中文文档与社区，助你快速掌握LLM应用开发

Type-safe Rust library for building AI agents across 20+ providers

Document-aware AI editing SDK for rich-text editors

GoAI SDK: one unified Go API across 25+ LLM providers with streaming, structured output, MCP support.