google--adk-python/contributing/samples/workflows/node_as_tool

Node as Tool

Overview

Demonstrates wrapping both a regular ADK Node (using the @node decorator) and a Workflow as tools that can be automatically called by a parent Agent.

It also demonstrates how a node-based tool can pause execution for Human-in-the-Loop (HITL) input using RequestInput and resume dynamically.

In this sample:

1. The parent agent receives an inquiry about a customer's discount.
2. It invokes customer_lookup_workflow (a Workflow wrapped as a tool) to retrieve customer status.
3. It then invokes calculate_discount (a regular Node wrapped as a tool) using the retrieved status.
4. If the customer is a VIP, calculate_discount yields a RequestInput event to ask for confirmation. The invocation pauses and is resumed once the user provides input.

Sample Inputs

• What discount does customer c123 get?

  This is a multi-turn interaction demonstrating Human-in-the-Loop:

  • Turn 1: The parent agent invokes customer_lookup_workflow to verify status, then invokes calculate_discount. calculate_discount yields a RequestInput asking "Apply VIP discount for tier 'Verified VIP Member'?", which pauses the run.
  • Turn 2: Respond with yes to resume the run. It calculates the "20% off" discount, and the parent agent summarizes the results.

Agent Topology Graph

graph TD
    customer_service_agent[customer_service_agent] -->|calls| customer_lookup_workflow(customer_lookup_workflow)
    customer_service_agent -->|calls| calculate_discount(calculate_discount)

How To

To expose an existing Node or Workflow as a tool callable by an Agent:

1. Define your Node (or @node) or Workflow and assign both an input_schema and a description.
2. Pass the node/workflow directly into your parent agent's tools list: Agent(..., tools=[my_node, my_workflow]).

Related Guides

• Workflow - Explains building complex multi-step graphs.