are you minting with collection_id in the ordinals metadata…

Yes, The whole point of the protocol is that it is open, no walled gardens.

With just the collection_id one can retrieve all required data about the collection from the indexers.

so to add to an existing collection you just mint with the same collection id?

if so, doesnt that mean anyone can add to your collection?

Once you've created the cover, go to 1SatOrdinals and copy the Inscription Origin Address.
- Select "Collection Items" and enter the Item name, Inscription Origin Address, and Item number