ADK Agent Builder

Read only the reference that matches the task. Loading the whole tree costs context and buries the part that matters.

Every API below was checked against google-adk 2.6.2. If a symbol is missing at runtime, read the source under src/google/adk/ rather than guessing a neighbouring name.

Start here

Task	Reference
First agent, environment, adk CLI	getting-started.md
Which import path is the canonical one	import-paths.md
The rules that cause most runtime failures	best-practices.md

Building blocks

• tool-catalog.md — function tools, MCP, OpenAPI, Google API toolsets, built-in tools, custom BaseTool and BaseToolset.
• function-nodes.md — plain functions as nodes: parameter resolution, generators, node_input typing rules.
• llm-agent-nodes.md — an LlmAgent used as a workflow node: output types, instruction templates, output_schema, auto-wrapping behavior.
• task-mode.md — mode='task' and mode='single_turn' delegation with schema-validated input and output.

Graph orchestration

• routing-and-conditions.md — routed edges, dict routing maps, default routes, self-loops, revision loops.
• parallel-and-fanout.md — fan-out edges, JoinNode fan-in, parallel_worker=True list processing.
• dynamic-nodes.md — scheduling nodes at runtime with ctx.run_node() and imperative workflow construction.
• human-in-the-loop.md — RequestInput, resume behavior, resumable vs replayed sessions.
• advanced-patterns.md — nested workflows, retries, custom BaseNode subclasses, graph validation rules.
• multi-agent.md — chat-transfer hierarchies, and the deprecated SequentialAgent / LoopAgent / ParallelAgent shells that Workflow replaces.

Runtime and verification

• state-and-events.md — the Context object, Event fields, and how state flows between nodes.
• session-and-state.md — session services, artifacts, memory, and state key scoping.
• callbacks-and-plugins.md — the six agent callbacks and app-level plugins.
• testing.md — pytest with InMemoryRunner, faking a model, asserting on node output.