Google Agent Development Kit (ADK) vs Letta
A side-by-side comparison of capabilities, autonomy, integrations, and pricing to help you choose.
Short answer: choose Google Agent Development Kit (ADK) if you want open-source framework for building and orchestrating multi-agent systems (Supervised agent, free); choose Letta if you want open-source framework for stateful ai agents with long-term memory (Supervised agent, freemium).
| Google Agent Development Kit (ADK) | Letta | |
|---|---|---|
| What it is | Open-source framework for building and orchestrating multi-agent systems | Open-source framework for stateful AI agents with long-term memory |
| Type | framework | framework |
| Autonomy | Supervised agent | Supervised agent |
| Pricing | free · Free (open source; pay model + cloud usage) | freemium · Free (open source); Cloud Pro $20/mo + usage |
| Best for | developers, enterprise | developers |
| Deployment | self-hosted, api | self-hosted, saas, api |
| Modalities | text, code, api | text, code, api |
| Models | gemini, model-agnostic | model-agnostic, gpt, claude, open-source |
| Protocols | a2a, mcp, function-calling, rest-api | mcp, rest-api |
| Integrations | Vertex AI, Cloud Run, Gemini, LiteLLM, MCP servers | MCP servers, OpenAI, Anthropic, Ollama, custom tools |
| Capabilities | 3 documented | 4 documented |
Google Agent Development Kit (ADK)
- +Backed by Google with first-class deployment to Vertex AI and Cloud Run
- +Built around the open A2A protocol for cross-framework agent interoperability
- +Model-agnostic via LiteLLM despite Gemini-first defaults
- -A framework, not a product: you build, host, and secure agents yourself
- -Strongest when paired with Google Cloud, which can imply lock-in
Letta
- +Genuinely differentiated memory architecture (self-editing memory blocks from MemGPT research, not a RAG wrapper)
- +Open source under Apache-2.0, self-hostable, and model-agnostic, which avoids lock-in
- +Strong developer ergonomics: REST API, Python and TypeScript SDKs, and the ADE GUI with deep state visibility
- -Positioning has become muddy across research lab, stateful-agents platform, and a Letta Code coding agent
- -Real usage costs climb well beyond the $20 Pro tier once LLM token pass-through is counted
Which should you choose?
Google Agent Development Kit (ADK) is open-source framework for building and orchestrating multi-agent systems, best for developers, enterprise. Letta is open-source framework for stateful ai agents with long-term memory, best for developers. The right choice depends on the autonomy level you want, your existing integrations, and your budget, all compared above.