It violates the TileJSON spec, but Mapbox Studio Classic expects an object with a key of vector_layers in https://maps.wikimedia.org/osm-pbf/info.json
The usual way to do this is have a fields key in the yaml for each layer, e.g.
- id: landmark_polygon
Datasource:
table: ...
type: postgis
minzoom: 6
description: Area features for background drawing
fields:
landmark: Landmark type
properties:
"buffer-size": 2
srs: +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +overThis then gets added to the tilejson by the serving software.
See https://phabricator.wikimedia.org/T159631#3079076 and https://phabricator.wikimedia.org/T159631#3080107 for more details