Proper way to use tools inside Custom Agents

[tiagopvianna]

Hello everyone!

I’m exploring how to properly use tools inside custom BaseAgent implementations and haven’t found clear guidance in the official docs or samples—only patterns for sub‑agents.

The closest analogy is how custom agents define sub-agents like this, can we apply the same approach to tools?

custom_agent = CustomAgent(
    name = "custom_agent",
    sub_agent_1 = sub_agent_1,
    tool_1 = tool_1
)

Imagine doing this in init:

class CustomAgent(BaseAgent):
    sub_agent_1: Agent
    tool_1: FunctionTool

    def __init__(self, name: str, sub_agent_1: Agent, tool_1: FunctionTool):
        super().__init__(name=name, sub_agent_1=sub_agent_1, tool_1=tool_1)
        self.sub_agent_1 = sub_agent_1
        self.tool_1 = tool_1

… and then invoking the tool inside _run_async_impl:

tool_ctx = ToolContext(invocation_context = ctx)
args = {"arg_1": arg_1}
result = await self.tool_1.run_async(
    args=args,
    tool_context=tool_context,
)

Does this align with ADK’s intended usage?

Thank you!