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

ADK Workflow Request Input Sample

Overview

This sample demonstrates how to create a Human-in-the-Loop workflow in ADK Workflows using the RequestInput event.

It shows a customer support scenario where an LLM agent (draft_email) drafts a response to a customer complaint. The workflow then halts execution and prompts a human user for review (request_human_review). Depending on the human's input (approve, reject, or custom feedback), the workflow either completes, aborts, or loops back to the AI for revisions.

This pattern is crucial for tasks where AI actions require human verification before proceeding.

Sample Inputs

• My phone battery drains too fast

• I never received my order

• The software crashes when I open the settings

Graph

graph TD
    START --> draft_email
    draft_email --> request_human_review
    request_human_review --> handle_human_review
    handle_human_review -->|revise| draft_email
    handle_human_review -->|approved| send_email
    handle_human_review -->|rejected| END_rejected[END rejected]

How To

1. Yield a RequestInput event from a node to halt the workflow and prompt the user for input.

   from google.adk.events import RequestInput
   
   def request_human_review(draft: str):
       yield RequestInput(
           message="Please review the draft...",
       )
   

2. The subsequent node will receive the user's input as its argument (node_input). You can use this input to determine the next routing step.

   def handle_human_review(node_input: str):
       if node_input == "approve":
           yield Event(route="approved")
       elif node_input == "reject":
           yield Event(route="rejected")
       else:
           yield Event(state={"feedback": node_input}, route="revise")
   

3. Define the edges in your workflow to handle the different routes, including looping back for revisions.

   Workflow(
       name="request_input",
       edges=[
           ("START", ..., draft_email, request_human_review, handle_human_review),
           (handle_human_review, {"revise": draft_email, "approved": send_email}),
       ],
   )