The metadata table is used as a key/value store for settings. It MUST contain these two rows:
name (string): The human-readable name of the tileset.
format (string): The file format of the tile data: pbf, jpg, png, webp, or an IETF media type for other formats.
According to https://github.com/mapbox/mbtiles-spec/blob/master/1.3/spec.md a MBTiles
format
is currently missing