Human-in-the-Loop AI Agents with Google ADK and Telegram

Google's Agent Development Kit (ADK) ships with a human_in_loop sample that demonstrates the concept of pausing an agent for human approval. It's a great starting point for understanding the mechanics. This post builds on that concept with a chat UI where users submit requests, the agent decides if it needs human review, and a Telegram message lands in a manager's phone with Approve / Reject buttons — closer to how this pattern would feel in real usage. Here's how I built it. The Original Sample — What It Shows The original sample teaches a critical ADK concept: long-running tools . A normal ADK tool returns a result immediately. A LongRunningFunctionTool returns a preliminary response ( status: pending ) and then expects your application to feed back an updated response later—once the external process (a human, a webhook, a queue) completes. The sample agent is a reimbursement bot: root_agent = Agent ( model = ' gemini-2.5-flash ' , name = ' reimbursement_agent ' , instruction = """ I