How to differentiate NFTs of the same policy id?

Question

For Example:

You have an NFT collection that has 5 different tiers all under the same policy ID (cip-25 metadata standard). You want to be able to provide on-chain benefits to holders of the NFT dependent on the tier they hold.

Because each tier shares the same policy ID what is the easiest way to categorize and reward the different tiers?

The solution that comes to my mind is having 1 piece of the NFTs metadata mention its tier, then using blockfrost to take a policy ID snapshot that sorts by tier name.

Answer 1

You can add custom metadata to your NFT. The most used standard is CIP-721.

The metadata could look like this:

{
  "721": {
    "<policy_id>": {
      "<asset_name>": {
        "name": <string>,
        "image": <uri | array>,
        "tier": 1 
      }
    }
  }
}

As you mentioned you could then use an API like blockfrost or Koios to get the metadata, check the tier property and do whatever you want with that information.

Answer 2

You could build a Merkle tree of asset names for each tier and encode the root hash in the smart contract. In the redeemer you give the correct intermediate hashes (public), compute the root hash and verify with the tier root hash.