Parellel FunctionTool Call

[sahilzs8]

Hi,
I have built a multi-agent system where there's a root agent and it has sub-agents with generator and reviewer.
The root agent to use these subagents as FunctionTool, now i want my root agent to call these tools in parallelly.
since these are not just python logic functions/ API functions....rather it's a agent as a function to the root agent.
So for this case how can i implement the tool call parallelly?

[adk-bot]

Response from ADK Answering Agent (experimental, answer may be inaccurate)

TLDR: Yes, the ADK supports parallel tool calls for sub-agents. To enable this, you must ensure your sub-agents are implemented as asynchronous tools.

---

Hello! That's an excellent question about architecting multi-agent systems with ADK.

ADK is designed to improve performance by automatically running multiple tool calls in parallel whenever the model requests them in a single turn. This applies to any FunctionTool, including a sub-agent wrapped as a tool.

The key requirement to unlock this parallel execution is to build your tools for asynchronous operation [1]. Here’s how you can apply this to your scenario:

1. Asynchronous Sub-Agents: The function that invokes your sub-agent (which is then wrapped by FunctionTool) must be defined as an async function. The ADK runner uses an asyncio event loop to run these async tools concurrently.

2. Non-Blocking Code: Inside your sub-agents, it's crucial to use non-blocking I/O operations. For example, if your sub-agent needs to wait or simulate work, it should use await asyncio.sleep(seconds) instead of the synchronous time.sleep(seconds). Using a synchronous call will block the entire execution thread, preventing any other tool from running in parallel.

Example

The ADK includes a sample agent specifically to demonstrate and test parallel function execution. This sample is a great reference for seeing how to structure async tools correctly.

You can find this sample and detailed explanations in the ADK repository [2]. It shows the performance difference between parallel and sequential execution and provides a clear pattern for implementation.

By ensuring your sub-agent tools are fully asynchronous, you should be able to achieve the parallel execution you're looking for.

[1] https://google.github.io/adk-docs/tools/performance/
[2] https://github.com/google/adk-python/blob/main/contributing/samples/parallel_functions/README.md