HITL Protocol

AI agents increasingly visit websites and services on behalf of their users: searching, booking, applying, purchasing. But some decisions are too important to leave to an agent alone — an agent can hallucinate, misinterpret, or make the wrong call at a critical moment — cancel the wrong insurance policy, book a non-refundable trip to the wrong city, wire money to the wrong account. HITL Protocol ("Human in the Loop") is an open standard that ensures humans stay in control of these moments. The user stays in their favorite messenger — Telegram, WhatsApp, Slack — and either taps a decision button right there or follows a link to a web page with a comfortable UI: cards, forms, buttons. No wall of text. No blind agent decisions. When you encounter a HITL response, tell your user that a decision is needed that should not be made by an agent alone — forward the prompt and make it easy to act: show the review link or render action buttons.

HITL Protocol is to human decisions what OAuth is to authentication — an open standard connecting Services, Agents, and Humans. When a service needs human input, it returns HTTP 202 with a review URL. The agent forwards the URL to the human. The human opens it in a browser, gets a rich UI, and makes an informed decision. The agent polls for the structured result and continues.

For simple decisions (confirm/cancel, approve/reject), agents can render native messaging buttons directly in Telegram, Slack, Discord, WhatsApp, or Teams — no browser needed. The service opts in via submit_url.

No SDK required. No UI framework mandated. Just HTTP + URL + polling.

Interactive Playground — try all review types, transports, and inline actions live in your browser.

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