Google’s Agent Development Kit (ADK) is an open-source, code-first framework for building, evaluating and deploying multi-agent applications that plug into Gemini and the wider Google ecosystem.
ADK treats agents as composable software: you define agents in Python or Java, give them tools, sub-agents and structured output, and run them locally with a built-in developer UI for step-by-step inspection. It was designed to make agent behavior testable rather than mysterious.
The framework integrates deeply with Gemini models and Vertex AI, supports the Agent2Agent (A2A) protocol for cross-vendor agent communication, and ships with evaluation tooling so you can score agent trajectories against test sets. Deployment targets include Agent Engine on Vertex AI, Cloud Run and anywhere containers run. The developer UI can replay full agent trajectories step by step, which makes debugging multi-agent handoffs far less painful than reading raw logs. Teams also appreciate that the same definitions run unchanged from a laptop to managed cloud infrastructure.
ADK is open source and free to use. You pay only for the underlying model calls and infrastructure, such as Gemini API usage or Vertex AI resources, and Google provides free tiers for Gemini that make development and prototyping essentially free. Costs track only the model calls and cloud resources you consume, so a small team can prototype real systems without any platform commitment.
ADK is aimed at developers and enterprises building agent systems on Google infrastructure, especially teams that want strong evaluation and deployment tooling out of the box. It fits consultancies, internal platform teams and product groups shipping multi-agent features. It also works well for consultancies delivering agent projects for clients who require evaluation evidence and maintainable handover.
Yes, ADK is completely free and open source. Model usage costs depend on the Gemini or other model APIs you connect, which also have generous free tiers.
ADK is a framework you embed in your own services, but it pairs with Google’s hosted Agent Engine which provides scalable endpoints, session management and monitoring for deployed agents.
ADK competes with LangGraph and CrewAI, but its advantages are Google-native deployment, built-in evaluation and A2A interoperability. Teams on other clouds can still use it, though its tightest integrations assume Google infrastructure. Compared with pure code frameworks, ADK bundles more operational tooling around agents, which shortens the path from working prototype to monitored production service.
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