A rich ecosystem of frameworks supports agent development. LangGraph, from the LangChain team, builds stateful multi-step agent workflows as directed graphs with nodes representing actions and edges representing transitions. AutoGen, a Microsoft framework, specializes in multi-agent conversational systems where agents chat with each other to solve tasks. CrewAI orchestrates role-playing agents that work together as a crew with defined roles, goals, and tasks. The OpenAI Agents SDK is an open-source Python library supporting tool use, handoffs, guardrails, and tracing, with handoffs being a mechanism to transfer control between specialized agents. Google's Agent Development Kit (ADK) provides built-in support for multi-agent orchestration and tool use, while Microsoft Semantic Kernel uses plugins (collections of native or LLM functions) and a planner component to create execution plans from available plugins.
Data-focused frameworks add specialized retrieval capabilities. LlamaIndex connects LLMs to external data, often building RAG-powered agents with structured data access through query engines used as tools. Haystack, by deepset, builds production-ready LLM applications including RAG pipelines and modular agents. DSPy algorithmically optimizes LLM prompts and weights, systematically improving agent behavior rather than relying on manual prompt engineering. Lightweight options include smolagents from Hugging Face, which focuses on code-based tool calling where the LLM writes Python code as actions rather than structured JSON. TapeAgents, by ServiceNow, structures computation as a persistent, replayable tape of thoughts, actions, and observations that doubles as execution trace and memory.
Managed cloud platforms abstract away much of the infrastructure. OpenAI's Assistants API provides persistent conversation threads, a sandboxed Code Interpreter tool, file search, and function calling. The newer Responses API combines Chat Completions simplicity with built-in tool support including web search, file search, and computer use. Anthropic offers Claude with function calling plus specialized tools like computer use for GUI control, text_editor for file modifications, and bash for shell execution. Amazon Bedrock Agents orchestrate multi-step tasks using foundation models with enterprise data, while Google's Vertex AI Agent Builder provides a managed platform with Google Cloud integrations.