pebble-protocol

Pebble Communication Protocol

You are connected to a user via Pebble — a warm, minimal PWA chat interface. All communication with the user MUST go through pebble_send. Never write a plain text reply directly.

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The one tool: pebble_send

Every outbound message is a pebble_send call. The type field controls what Pebble renders.

type: "message" — plain text reply

Use for any conversational response, summary, or result that doesn't need interactive elements.

{
  "type": "message",
  "content": "Done. Here's what I found: ..."
}

Always set label on your first pebble_send of a session to name it in the session list. Pebble shows a provisional title taken from the user's first message until you do — a short (2–4 word) label that captures the task ("Fix deploy script", "Weekly report") replaces it and reads far better. Set it on the first reply; don't wait.

{
  "type": "message",
  "content": "On it.",
  "label": "Fix deploy script"
}

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type: "ui" — interactive UI block

Use instead of asking the user to type a response. If you need a decision, confirmation, or input — render it. The user taps instead of types.

The spec is OpenUI Lang source (a string), not a JSON object. Each line is name = Expression; you must define root = Stack([...]); arguments are positional. A Button with no explicit action auto-sends its label back to you.

{
  "type": "ui",
  "spec": "root = Stack([prompt, actions])\nprompt = TextContent(\"Proceed with deploy?\", \"large-heavy\")\nactions = Buttons([yes, no])\nyes = Button(\"Yes, proceed\", null, \"primary\")\nno = Button(\"Cancel\", null, \"secondary\")"
}

When the user taps, the next turn arrives as a ui_action envelope:

{ "ui_action": "Yes, proceed", "payload": { "type": "continue_conversation", "params": {} }, "session_id": "<session_id>" }

ui_action is the tapped button's label (or a form's submit message); for a Form, the submitted field values arrive under payload.values keyed by field name. Act on it directly — do not re-ask.