Spec: yodel.purpose — semantic category for interaction intent (separate from device.type)

[rolpro]

Motivation

device.type describes hardware (ios, android, car). But a walkie-talkie runs on iOS — the platform says nothing about the interaction mode. Voice-only clients need different responses than display clients, regardless of OS.

Proposal: yodel.purpose + yodel.purpose_override

Two new optional fields in the Yodel block:

purpose — selects the base profile

{
  "yodel": {
    "purpose": "walkie-talkie",
    "device": {
      "type": "ios"
    }
  }
}

The gateway uses purpose to load a base system prompt from the prompts repository (openyodel/prompts). It describes the fundamental interaction mode.

purpose_override — refines the profile (optional)

{
  "yodel": {
    "purpose": "walkie-talkie",
    "purpose_override": "Sprich wie ein Offizier. Kurze Befehle."
  }
}

Appended to the base prompt. Allows the client (or end user) to customize behavior without replacing the whole system prompt. Free-form string, not an enum — supports combinations and nuance that a tag system can't capture.

Gateway behavior

1. Load base prompt from openyodel/prompts using purpose as key
2. If purpose_override is set → append it
3. If purpose is absent → neutral default
4. If purpose_override is set without purpose → append to neutral default

Proposed purpose values

purpose	Typical Device	Response Style
walkie-talkie	PTT handset, radio app	Spoken, no markdown, quick exchanges
dashboard	Car display	Glanceable, max 1 sentence
big-screen	Stadium LED, billboard	Large, high contrast
smartwatch	Watch	Ultra-short, notification style
tv	Television, Apple TV	Readable from 3m
terminal	CLI, desktop agent	Markdown, code, full scope
chat	Messenger, chat app	Hybrid: short answers, markdown ok
dictation	Voice recorder	Formal, punctuated, full sentences
kiosk	Info terminal	Structured, button-friendly
speaker	Smart speaker	Spoken, longer than walkie-talkie
headset	Headphones, earbuds	Spoken, intimate, short

Distinction from device.type

• device.type = hardware platform (audio codecs, capabilities)
• purpose = why is the user talking to the agent?
• purpose_override = how should the agent adapt?
• All three complement each other

Open questions

• Should purpose be required or optional? (Proposal: optional)
• Valid values: open registry or spec-defined enum? (Proposal: spec-defined with extensibility path)

References

• moongrabber/wire-walkie-swift#77 — Client-side usage
• Feature: Default system prompts per yodel.purpose plugin-openyodel-hermes#22 — Gateway defaults per purpose
• Bootstrapping: Repo structure + initial purpose prompts prompts#1 — Prompt content repository

[rolpro]

Prompt-Repo: openyodel/prompts#1 — spezifiziert die konkreten Prompts pro purpose, getrennt von der Protokoll-Spec.