# Convention for declaring filters of an NFT

## Abstract

The goal is to establish a standard for how filters are declared inside a non-fungible (NFT) metadata.

## Specification

The key words “ **MUST**”, “ **MUST NOT**”, “ **REQUIRED**”, “ **SHALL**”, “ **SHALL NOT**”, “ **SHOULD**”, “ **SHOULD NOT**”, “ **RECOMMENDED**”, “ **MAY**”, and “ **OPTIONAL**” in this document are to be interpreted as described in [RFC-2119](https://www.ietf.org/rfc/rfc2119.txt).

> Comments like this are non-normative.

If the property `filters` is provided anywhere in the metadata of an nft, it **MUST** adhere to the schema below.
If the nft is a part of a larger collection and that collection has filters, all the available filters for the collection **MUST** be listed as a property of the `filters` object.
If the nft does not have a particular filter, it’s value **MUST** be “none”.

The JSON schema for `filters` is as follows:

```
{

"title": "Filters for Non-Fungible Token",

"type": "object",

"properties": {

"filters": {

"type": "object",

"description": "Filters can be used to filter nfts of a collection.  Values must be an array of strings or numbers."

}

}

}
```

#### Examples

##### Example of an NFT that has traits & filters

```
{

"name": "NFT With Traits & filters",

"description": "NFT with traits & filters",

"image": "https://s3.amazonaws.com/your-bucket/images/two.png",

"image_integrity": "sha256-47DEQpj8HBSa+/TImW+5JCeuQeRkm5NMpJWZG3hSuFU=",

"properties": {

"creator": "Tim Smith",

"created_at": "January 2, 2022",

"traits": {

"background": "yellow",

"head": "curly"

},

"filters": {

"xp": 120,

"state": "REM"

}

}

}
```

## Rationale

A standard for filters is needed so programs know what to expect in order to filter things without using rarity.

## Backwards Compatibility

If `filters` wants to be added on top of fields [ARC-16](https://dev.algorand.co/arc-0016)`traits` and `filters` should be inside the `properties` object. (eg: [Example above](https://dev.algorand.co/arc-standards/arc-0036#example-of-an-nft-that-has-traits--filters))

## Security Considerations

None.

## Copyright

Copyright and related rights waived via [CCO](https://creativecommons.org/publicdomain/zero/1.0/).