SillyTavern V2 Open Spec Technical Documentation

1. Root Object Structure

V2 character cards require a top-level wrapper with spec: "chara_card_v2" and spec_version: "2.0". All character attributes are encapsulated inside the data dictionary.

{
  "spec": "chara_card_v2",
  "spec_version": "2.0",
  "data": {
    "name": "Character Name",
    "description": "Character Overview",
    "personality": "W++ specs",
    "scenario": "RP Scenario",
    "first_mes": "First Message",
    "mes_example": "<START>\n{{user}}: Hi\n{{char}}: Hello!",
    "creator_notes": "Author Notes",
    "system_prompt": "",
    "post_history_instructions": "",
    "tags": ["Fantasy", "Action"],
    "creator": "Creator Name",
    "character_version": "1.0",
    "alternate_greetings": [],
    "extensions": {}
  }
}

2. Reserved Macro Tokens

• {{user}}: Dynamically replaced with the current user's display name.
• {{char}}: Dynamically replaced with the character's data.name.
• <START>: Delimits separate dialogue example turns inside mes_example.

3. Token Gauge Calculation Algorithm

For standard BPE tokenizers (e.g. Llama, Claude, GPT-4), the estimated token length is calculated using the weighted sum of character lengths across active prompt fields divided by a factor of 4.