bookstack/dev/api/requests/chapters-create.json

{
  "book_id": 1,
  "name": "My fantastic new chapter",
  "description_html": "<p>This is a <strong>great new chapter</strong> that I've created via the API</p>",
  "priority": 15,
  "default_template_id": 25,
  "tags": [
    {"name": "Category", "value": "Top Content"},
    {"name": "Rating", "value": "Highest"}
  ]
}