Events¶
Events are the fundamental units of information flow within the Agent Development Kit (ADK). They represent every significant occurrence during an agent's interaction lifecycle, from initial user input to the final response and all the steps in between. Understanding events is crucial because they are the primary way components communicate, state is managed, and control flow is directed.
What Events Are and Why They Matter¶
An Event in ADK is a record representing a specific point in the agent's execution. It captures user messages, agent replies, requests to use tools (function calls), tool results, state changes, control signals, and errors.
Technically, it's an instance of the google.adk.events.Event class, which builds upon the basic LlmResponse structure by adding essential ADK-specific metadata and an actions payload.
# Conceptual Structure of an Event (Python)
# from google.adk.events import Event, EventActions
# from google.genai import types
# class Event(LlmResponse): # Simplified view
# # --- LlmResponse fields ---
# content: Optional[types.Content]
# partial: Optional[bool]
# # ... other response fields ...
# # --- ADK specific additions ---
# author: str # 'user' or agent name
# invocation_id: str # ID for the whole interaction run
# id: str # Unique ID for this specific event
# timestamp: float # Creation time
# actions: EventActions # Important for side-effects & control
# branch: Optional[str] # Hierarchy path
# # ...