# Google Agent Development Kit
The Google Agent Development Kit (ADK) is an open-source, code-first framework from Google for building, evaluating, and deploying AI agents, and multi-agent systems, introduced at Google Cloud NEXT 2025 in April 2025.[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/) It sits between the Gemini models it is optimized for and the Google Cloud services that host finished agents: ADK is the development framework, Vertex AI Agent Engine is a managed deployment runtime for it, and the [Agent2Agent](https://www.edgepedia.org/agent2agent) (A2A) protocol is a separate specification for agent-to-agent communication that ADK agents can speak.
| Fact | Detail |
|---|---|
| Announced | Google Cloud NEXT 2025, April 2025[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/) |
| License | Apache License 2.0[2](https://github.com/google/adk-docs) |
| Languages | Python (v1.0.0 stable, May 2025); Java (v0.1.0, May 2025)[3](https://developers.googleblog.com/en/agents-adk-agent-engine-a2a-enhancements-google-io/) |
| Model support | Optimized for Gemini and Vertex AI; model-agnostic via LiteLLM[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/) |
| Deployment targets | Any container runtime, Cloud Run, GKE, Vertex AI Agent Engine[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/) • [4](https://adk.dev/) |
| Current major version | ADK 2.0, with breaking API and session changes from 1.x[5](https://github.com/google/adk-python) |
## What it is
ADK is a developer toolkit, not a model or a hosted service. Google describes it as an "open-source, code-first toolkit for building, evaluating, and deploying sophisticated AI agents with flexibility and control," licensed under Apache 2.0.[2](https://github.com/google/adk-docs) Agents are written as code rather than configured in a visual editor, and the framework handles the plumbing that single-model SDK calls do not: orchestrating multiple agents, binding tools, managing conversation state, and packaging the result for deployment.[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/)
Although optimized for Gemini and [Vertex AI](https://www.edgepedia.org/vertex-ai), the project states it is model-agnostic and deployment-agnostic, and compatible with other frameworks.[5](https://github.com/google/adk-python) LiteLLM integration lets developers call models from [Anthropic](https://www.edgepedia.org/anthropic), Meta, Mistral AI, AI21 Labs, and others, and ADK can incorporate tools and agents from [LangChain](https://www.edgepedia.org/langchain), LlamaIndex, LangGraph, and CrewAI.[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/)
## Launch and version history
Google introduced ADK at Google Cloud NEXT 2025 in April 2025 as a framework designed to "simplify the full stack end-to-end development of agents and multi-agent systems."[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/) The documentation repository was created on 2025-04-01.[2](https://github.com/google/adk-docs)
At [Google I/O](https://www.edgepedia.org/google-i-o) in May 2025, Google announced Python ADK v1.0.0, calling it a stable, production-ready release, and launched Java ADK v0.1.0.[3](https://developers.googleblog.com/en/agents-adk-agent-engine-a2a-enhancements-google-io/) A later ADK 2.0 release introduced breaking changes to the agent API, event model, and session schema; sessions written by ADK 2.0 are readable by ADK 1.28 and later (extra fields are ignored) but are incompatible with older 1.x versions.[5](https://github.com/google/adk-python)
## How it works
ADK offers two styles of composition. **Workflow agents** give deterministic pipelines: `Sequential`, `Parallel`, and `Loop` agents execute fixed structures, useful where predictability matters. `LlmAgent` transfer provides LLM-driven dynamic routing for adaptive behavior, letting a model decide which sub-agent handles a request.[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/) Agents can be nested into hierarchies, so a coordinator agent can delegate to specialist agents.[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/)
The ADK 2.0 generation adds a graph-based Workflow Runtime, a graph execution engine for deterministic flows supporting routing, fan-out/fan-in, loops, retry, state management, dynamic nodes, human-in-the-loop steps, and nested workflows. A Task API provides structured agent-to-agent delegation with multi-turn task mode, single-turn controlled output, mixed delegation patterns, human-in-the-loop, and task agents usable as workflow nodes.[5](https://github.com/google/adk-python)
Tool binding covers pre-built tools such as web search and code execution, [Model Context Protocol](https://www.edgepedia.org/model-context-protocol) (MCP) tools, and third-party framework tools.[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/) For context management, ADK automatically filters irrelevant events, summarizes older conversational turns, lazy-loads artifacts, and tracks token usage.[4](https://adk.dev/) For development, the framework ships a [command-line interface](https://www.edgepedia.org/command-line-interface) and a visual web UI for local testing, plus built-in bidirectional audio and video streaming for voice and video agents.[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/)
## Evaluation and observability
Before deployment, ADK's built-in evaluation runs agents against predefined test cases through `AgentEvaluator.evaluate()`, assessing both the final response quality and the step-by-step execution trajectory, usable from the CLI or the web UI.[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/)
After deployment to Google Cloud via Agent Runtime, Cloud Run, or GKE, agents inherit managed infrastructure, built-in authentication, Cloud Trace observability, and what Google calls enterprise-grade security.[4](https://adk.dev/) The Vertex AI Agent Engine console gained a UI for viewing deployed agents, listing sessions, tracing, and monitoring.[3](https://developers.googleblog.com/en/agents-adk-agent-engine-a2a-enhancements-google-io/) These descriptions are Google's own; no independent assessment of the evaluation tooling's maturity appears in the available sources.
## Deployment and pricing
The framework itself is free, open-source software under Apache 2.0.[2](https://github.com/google/adk-docs) ADK can be deployed to any container runtime, or to Google Cloud paths: Vertex AI Agent Engine as a fully managed runtime, Cloud Run, or GKE.[1](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/) • [4](https://adk.dev/)
## A2A and interoperability
ADK's "native A2A support" refers to the Agent2Agent protocol, a separate Google-originated specification for how agents from different systems discover each other and exchange tasks. Alongside ADK's I/O 2025 updates, Google released A2A protocol specification v0.2, adding stateless interaction support and OpenAPI-like standardized authentication, together with an official Python SDK for A2A.[3](https://developers.googleblog.com/en/agents-adk-agent-engine-a2a-enhancements-google-io/) Google announced third-party adoption: Microsoft said it would support the protocol in [Azure AI Foundry](https://www.edgepedia.org/azure-ai-foundry) for building A2A agents and allow invoking any A2A agent in [Microsoft Copilot Studio](https://www.edgepedia.org/microsoft-copilot-studio); SAP announced support in Joule; and Zoom announced support in its open platform.[3](https://developers.googleblog.com/en/agents-adk-agent-engine-a2a-enhancements-google-io/) These are vendor announcements of intent and support, not demonstrations of working cross-vendor deployments, and the sources do not cover A2A's reported donation to the [Linux Foundation](https://www.edgepedia.org/linux-foundation) or how A2A competes or coexists with MCP as a standard.
## By the numbers
All adoption figures available are vendor-side or repository statistics. The adk-docs repository, created 2025-04-01, had 1,481 stars and 212 open issues as of September 2026.[2](https://github.com/google/adk-docs) Google names Renault Group, Box, and Revionics as customers providing feedback on ADK.[3](https://developers.googleblog.com/en/agents-adk-agent-engine-a2a-enhancements-google-io/)
## References
1. [Agent Development Kit: Making it easy to build multi-agent applications - Google Developers Blog](https://developers.googleblog.com/agent-development-kit-easy-to-build-multi-agent-applications/)
2. [google/adk-docs](https://github.com/google/adk-docs)
3. [What's new with Agents: ADK, Agent Engine, and A2A Enhancements - Google Developers Blog](https://developers.googleblog.com/en/agents-adk-agent-engine-a2a-enhancements-google-io/)
4. [Agent Development Kit (ADK)](https://adk.dev/)
5. [google/adk-python](https://github.com/google/adk-python)
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*Topic: Encyclopedia › Technology and the built world › Computing and digital systems › Modern AI: foundation models, generative AI, and the AI industry › Foundation-model methods and training › Prompting, reasoning, and agents*
*Initially written Sep 17, 2026 · Edited: Oct 11, 2026; Oct 15, 2026*
*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*
License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license