Ranked · Agent frameworks
Best Agent frameworks — Open source
10 of 14 researched agent frameworks have a confirmed yes for Open source. Qualified, negative, and unknown answers stay distinct.
The ranking
10 of 14 agent frameworks have a confirmed yes for “Open source”. 3 are qualified or tier-scoped, 1 are confirmed no, and 0 remain not established. Only confirmed yes answers appear in this set; an unknown is never treated as a negative.
How we ranked these
Projected from the live listing datasheets using the tenant’s “Is the source available?” axis. Membership requires a sourced yes; partial and unknown answers are reported above but excluded from the ranking. Entries retain the directory’s paid-tier ordering, visibly labelled on every promoted card.
All picks at a glance
All 10 compared on one screen. Pick a row to jump to the full entry.
| # | Agent | Best for | From |
|---|---|---|---|
| 1 | Agent Development Kit (ADK) | Free | |
| 2 | AgentsKit.js | ||
| 3 | AutoGen | Free | |
| 4 | CrewAI | Free (month (50 workflow executions)) | |
| 5 | LangGraph | $0/seat/month | |
| 6 | Letta | $0 / month | |
| 7 | Mastra | Free | |
| 8 | Microsoft Agent Framework | Free | |
| 9 | OpenAI Agents SDK (Python) | Free | |
| 10 | Pydantic AI | Free |
The ranking
Editor’s pick
#1
Agent Development Kit (ADK)
Google's open-source framework for building, evaluating and deploying multi-agent systems.
- #2
AgentsKit.js
Composable TypeScript foundation for agent runtime, tools, memory, RAG and chat UI bindings.
- #3
AutoGen
Open-source Python and .NET framework for building single- and multi-agent AI applications; now in maintenance mode.
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CrewAI
Open-source Python framework for multi-agent crews, with a hosted platform for deploying and governing them.
- #7
Mastra
Open-source TypeScript framework for AI agents, with a hosted platform for observability and deployment
- #8
Microsoft Agent Framework
Open-source Microsoft SDK for building AI agents and multi-agent workflows in .NET, Python and Go.
- #9
OpenAI Agents SDK (Python)
MIT-licensed Python framework for multi-agent workflows, tools, guardrails and tracing
- #10
Pydantic AI
Typed Python agent framework: one agent definition, any model, terminal, web, editor or voice surface.
Side by side
All 10 compared. Scroll the table sideways, the fact column stays pinned →
| Feature | Agent Development Kit (ADK) | AgentsKit.js | AutoGen | CrewAI | LangGraph | Letta | Mastra | Microsoft Agent Framework | OpenAI Agents SDK (Python) | Pydantic AI |
|---|---|---|---|---|---|---|---|---|---|---|
| Description | Google's open-source framework for building, evaluating and deploying multi-agent systems. | Composable TypeScript foundation for agent runtime, tools, memory, RAG and chat UI bindings. | Open-source Python and .NET framework for building single- and multi-agent AI applications; now in maintenance mode. | Open-source Python framework for multi-agent crews, with a hosted platform for deploying and governing them. | MIT-licensed orchestration framework and runtime for stateful, long-running LLM agents. | Stateful agent harness with git-backed memory, run from a CLI, desktop app, web, or SDK | Open-source TypeScript framework for AI agents, with a hosted platform for observability and deployment | Open-source Microsoft SDK for building AI agents and multi-agent workflows in .NET, Python and Go. | MIT-licensed Python framework for multi-agent workflows, tools, guardrails and tracing | Typed Python agent framework: one agent definition, any model, terminal, web, editor or voice surface. |
| Category | Agent frameworks | Agent frameworks | Agent frameworks | Agent frameworks | Agent frameworks | Coding agents, Agent frameworks | Agent frameworks | Agent frameworks | Agent frameworks | Agent frameworks |
| Pricing | Free | - | Free | Free (month (50 workflow executions)) | $0/seat/month | $0 / month | Free | Free | Free | Free |
| API | Yes | Yes | No | Yes | Yes | Yes | Yes | Yes | Yes | No |
| Tags |
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- 10 agents ranked
- 8 of 8 with known API status offer an API
- paid plans $20-$250
- 8 free or freemium
- verified August 31, 2026
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